3 . Dr. David Sullivan, pediatric dentist（儿科牙医）, is just wild about teeth. So are some of his_________. Wild, that is. Really wild.

You see. Dr. David, as many people call him, has some_________patients. They aren’t the children he_________sees each day. They’re, well, big and hairy and sometimes weigh more than four hundred pounds. They’re_________animals.

On most days, Dr. David tends to his human patients, teaching them how to care for their_________.On some days, however, the Cincinnati Zoo calls with some special work for him to do. Since 1982, Dr. David has volunteered his time performing_________surgery on many of the animals. This would be a_________experience for most.

_________, Dr. David feels differently. “I’m not_________of the animals,” he says, “I have been around them so much that I'm used to them.” How does a children’s dentist find himself__________the teeth of a black rhino or a monkey? For Dr. David, it was a matter of__________

“When I was a kid in school, the only thing I ever__________to be was a veterinarian（兽医）,”says Dr. David, “I even applied to veterinary school in college.”

But Dr. David soon__________that veterinary work was__________for him. “I volunteered at a veterinarian’s office to get some experience,” he says, “I was__________I couldn’t breathe. My eyes were swollen shut. I had allergy symptoms（过敏症状）.”_______Dr. David tried pediatric dentistry and found he loved it.

After he became a dentist, Dr. David__________at Children's Hospital in Cincinnati, Ohio. While there, he was asked to help with dental work on some of the__________in the hospital’s research lab. It wasn’t long before he began a dental program for the animals.

Word of Dr. David’s work with animals__________, and soon King’s Island Amusement Park and the Cincinnati Zoo were calling to ask for his__________. Now he regularly gets calls from the zoo.

4 . Fire ants are famous for their construction projects (as well as their burning bites). When they need to, colonies of these insects turn themselves into ladders, chains and walls. And when flood water rises, a colony can float to safety by making an unusual boat. The ants hold tightly to each other, forming a floating disk atop the water. The antraft may float for months seeking safe harbor. The ants on the bottom don’t drown, and the ants on the top stay dry. Working together, the ants float to safety — even though a single ant alone in the water will struggle to survive.

“They have to stay together as a colony to survive.” Nathan Mlot said.

Fire ants and water don’t mix. The ant’s hard outer shell, naturally repels water. A drop of water can sit on top of the ant like a backpack. When an ant does end up underwater, tiny hairs on its body can trap bubbles of air that give the bug a boost up.

To investigate the science behind the antraft, the scientists placed hundreds or thousands of ants at a time in the water. A group of ants took about 100 seconds, on average, to build a raft. The researchers repeated the experiment multiple times. Each time, the ants organized themselves the same way, creating a raft about the size and the thickness of a thin pancake. The rafts were flexible and strong, staying together even when the researchers pushed the rafts underwater.

The scientists then froze the rafts in liquid nitrogen and studied them under powerful microscopes to figure out how the ants kept everyone safe and the water out.

The team found that some ants used their jaws to bite other ants’ legs. Other ants joined their legs together. Thanks to these tight bonds, say the scientists, the ants did a better job at keeping the water away than any one ant could do on its own. By working together, thousands of ants can stay alive in the face of a crisis like a flood by using their own bodies to build a boat.

5 . Animals might not be able to speak or master advanced language techniques, but they certainly have other ways of communicating. Whale song, wolf howls, frog cries — even the fast dance of the honeybee or the friendly waves of a dog’s tail — are among so many ways animals pass on information to each other and to other living things of the animal kingdom.

When it comes to hearing communication, not every member of a species is just alike. Animals in different places have often been sounding off in different dialects. For example, one study shows that blue whales produce different types of sounds depending on where they are from. Some bird species are the same way. And what about those birds that live on the border between territories (领地) of different songbirds? They are often able to communicate in a way accepted by each of their groups of neighbors.

Communication between different species can play important roles as well. One study shows that iguanas (鬣蜥蜴) do not communicate by making sound, but their well-developed ears help them hear well the warning calls of the flycatcher (a type of small bird). The two species have nothing in common except for the fact that they share a general habitat and enemies. So when an iguana hears a bird make a signal of danger for other birds, it probably knows to be watchful for arriving enemies, too.

However, as noise pollution has become a serious problem all across the globe, many animals are now under fire. Increased shipping traffic over the last century has greatly affected the spread of whale song around the ocean basin. Studies have found that songbirds, too, suffer from noisy city surroundings. Some species have had to change their singing styles, producing songs that sound louder, in order to be heard above the noise. Their new voices usually lead to stranger and somewhat worse styles of singing that female birds find decidedly less sexy.

6 . Priscilla Ouchida’s “energy efficient” house turned out to be a horrible dream. When she and her engineer husband married a few years ago, they built a $100,000 three-bedroom home in California. Tightly sealed to prevent air leaks, the house was equipped with small double-paned windows and several other energy-saving features. Problems began as soon as the couple moved in, however. Priscilla’s eyes burned. Her throat was constantly dry. She suffered from headaches and could hardly sleep. It was as though she had suddenly developed a strange illness.

Experts finally traced the cause of her illness. The level of formaldehyde gas in her kitchen was twice the maximum allowed by federal standards for chemical workers. The source of the gas? Her new kitchen cabinets and wall-to-wall carpeting.

The Ouchidas are victims of indoor air pollution, which is not given sufficient attention partly because of the nation’s drive to save energy. The problem itself isn’t new. “The indoor environment was dirty long before energy conservation came along,” says Moschandreas, a pollution scientist at Geomet Technologies in Maryland. “Energy conservation has tended to accentuate the situation in some cases.”

The problem appears to be more troublesome in newly constructed homes rather than old ones. Back in the days when energy was cheap, home builders didn’t worry much about unsealed cracks. Because of such leaks, the air in an average home was replaced by fresh outdoor air about once an hour. As a result, the pollutants generated in most households seldom built up to dangerous levels.

9 . Only humans speak using words. But all animals can communicate in one way or another. Maybe you have heard about the way bees dance around to send messages to each other and the way dogs make loud noises in different ways to give warnings.

Do you know that animals can communicate through infrasonic (次声的) sounds? This is how it works:

Humans hear low sounds like thunder rumbling (雷声轰鸣) in the sky. But we don’t hear sounds lower than these. However, elephants can hear many lower sounds, and they use them to communicate with each other. This is known as infrasound.

Another surprising thing about infrasound is that it travels over several kilometres. Sounds which have a higher pitch(音调), like the ones people can hear, don’t travel through walls, leaves, trees and so on. And that is why we can’t hear sounds from more than 100 metres away. But infrasound is much ‘stronger’, and things like grass and trees have no effect on it. Because of that it can travel much farther. Elephants can hear infrasonic calls from four kilometres away!

There have been reports that people were watching elephants feeding or resting when the elephants all ran away for no reason at all. It is clear that they heard a warning call from a long way away, but the people didn’t hear the sound. In places like a zoo where you can get nearer to animals, it is a bit easier to sense when infrasonic sounds are made. When you stand near mother elephants with their babies in a zoo you may notice a weak rumbling in the air every few minutes — not loud or strong, but clearly noticeable. They are infrasonic calls — the mother elephants “talking” to their babies.

10 . Wind power is a very clean source of energy. This is how wind power works. Wind makes windmills spin(旋转). When the windmills spin, they make electricity. Then we can use the electricity.

A lot of people think that wind power is new, but that’s not true. For thousands of years, people have used wind to sail boats and move water. We still do those things today, but these days we mostly use wind power to make electricity.

Wind power is a very popular source of energy. Most people think that we should use it more and more. First of all, it’s clean. Windmills don’t pollute the environment at all. Second, we can use wind power forever. After all, we will always have wind. Also, wind power is cheap, and it’s getting even cheaper.

A lot of people don’t understand wind power very well. They believe that there are problems with wind power, but many of those problems are not real. For example, some people say that windmills are dangerous for birds. They used to be true, but it isn’t true anymore. Old windmills killed birds because they spun very fast. New windmills spin slowly, and they aren’t dangerous for birds.

However, there are real problems with windmills. One problem is that many people think windmills are very ugly. This is a problem for people, because windmills are often in very pretty areas. Also, wind doesn’t blow all the time, so we can’t use wind power all the time. Finally, windmills are noisy.

Wind power is becoming more and more common. Right now, more than 80 countries use wind power. About 2.5 percent of the world’s power comes from the wind. For some countries, that number is a lot higher. Wind power gives Denmark more than 25 percent of its electricity.