4 . In 2009, Marina Ross, a psychologist at the UK's University of Portsmouth, conducted experiments in which she tickled（使发痒）monkeys. The monkeys responded by laughing.

Ross, who studies laughter, suggests we get our ability to laugh from humans and monkeys’ common ancestors, which lived 10 to 16 million years ago.

Now her latest study goes a step further, showing that monkeys display “laugh faces”—smiling with teeth bared—with or without actual laughter.

“This shows that monkeys can communicate in clearer and more versatile（多样化的）ways than we thought,” she says. “It’s similar to how people may smile silently while talking or laughing.”

Jaak Panskepp, a psychologist at Washington State University in Pullman, has found that tickled rats make happy noises. When scientists tickled the rats, they made the same sounds that they use during play. Some of the lab rats liked being tickled so much that they followed the hand that tickled them.

Since then, Panskepp and his colleagues have shown that studying play is serious business. They’ve found that the parts of rats’ brain responsible for laughter can be used to study human emotion. He’s also found seven basic emotional systems housed in the same areas of human brains.

His research has even helped fight depression in people One antidepressant（抗抑郁剂）in clinical trials, called GLYX-13, has its roots in the study of rat laughter.

“We think of rats and monkeys as smart, but intelligence isn’t a requirement for laughter,” Panksepp adds. “Maybe one should look at it the other way around, since it’s possible that play in any species can increase social intelligence.”

“So identifying other animals that laugh,” he says, “may be a matter of listening to the sounds they make while having fun.”

Who knows? One day we may discover an actual silly goose that laughs.

5 . A national park is created for the purpose of conservation. Yellowstone National Park in the US was the first national park in the world. Here are some other national parks in the world.

Northeast Greenland National Park, Denmark

The national park is the largest one in the world. It covers an area of 927，000 km²，It is also the most northern national park in the world.

Around 5,000 to 15,000 musk oxen (麝香牛) as well as polar bears live in the park. Some of the birds also live there.

Great Barrier Reef Marine Park, Australia

The park is the second largest national park in the world. It protects a large part of Australia’s Great Barrier Reef from being damaged in any way.

All commercial ships must stay on specific shipping routes that avoid the most sensitive areas of the park. The Great Barrier Reef has the world's largest number of corals and other sea life.

Great Limpopo Transfrontier Park, Mozambique

This national park covers an area of 99,800 km².It joins some of the famous wildlife areas in southern Africa into a huge conservation area.

In 2006, the Giriyondo tourist access between the Limpopo and Kruger national parks was opened. There were 5,000 animals moving from Kruger to Limpopo National Park, including over 1,000 elephants.

Wood Buffalo National Park, Canada

The park was created in 1922 to protect the wood bison (森林野牛) whose population had dropped from 40 million in 1830 to less than 1.000 by 1900.

The park consists of 44,807 square kilometers of northern plains. It is also the world's only natural living place of the cranes (鹤).

6 . Teenagers are in the age group of 13 to 19 years. The age group is thought to be the turning points of both boys and girls. They hardly take any notice of their health and they tend to eat junk food, have less sleep and more dangerously, try smoking, drinking and even drugs. All of these are bringing out many health problems to teenagers all around the world.

Researches show that 17.4 percent of the US teenagers are overweight, and the number of teenagers with diabetes and heart diseases is increasing rapidly. This is mainly due to the lack of proper food intake. Teenagers highly prefer fast and junk food which is the main reason for these health problems. Another problem faced by teenage girls is their need to be thin. This has been put into the teenage minds by the media. Girls tend to eat less and go or an unhealthy diet.

Teenagers are passing the most curious stage of their lives when they are eager to try out everything they see around them. This can be either in sexual activities or trying smoking drinking and drugs. The diseases caused by these factors can be deadly and incurable. Drinking, smoking and drugs can cause cancers and heart diseases. Sexually Transmitted Diseases(STD) are a major problem among teenagers. Diseases such as Hepatitis can be transmitted to another teenager by a simple kiss; AIDS is another high risk for teenagers when having sexual activities.

Teenagers are young; they have very little knowledge of these risk factors. It is up to us parents and teachers to guide them. They must have a good control of their lives, well-balanced diet and good exercise. Staying away from all bad habits such as drinking, smoking and sexual activities will give them a much happier and healthier life. We must help our kids to choose the correct path and become better citizens to the country and better humans to the world.

7 . How to Be a Good Tourist

Being a tourist means you start to experience different cultures, people and foods.     1     When you're visiting another country, it's your duty to make a good impression on the people there. So having a good knowledge of tour will make sure you'll be a good tourist no matter where you go.

Learn useful expressions in the language of the country you're going to.     2     While learning a new language is impossible for most people, learning some useful expressions in the local language is not. Pick up a translation book before you travel so you can remember some important expressions.

    3     Countries can have different kinds of climates. Before you visit another country or area, make sure that you know what the climate will be like so you can pack clothing that is suitable for the place you're visiting.

Do research on the country's customs and traditions. Being a good tourist includes being knowledgeable about the country you're visiting. You will also find out what the local clothing looks like so you can dress properly.     4    

Ask your tour guide questions. A tour guide is able to give you more knowledge of the country or city you're visiting.     5     You can ask your tour guide about local businesses or services you can use while you're visiting. Because your guide can be a native of the area, you can also ask him/ her about restaurants he / she prefers.

8 . Every day thousands of people travel across the world for different reasons. Whenever I've checked in for a flight, I've seen many travellers saying “I missed it” or “I forgot it”, etc. This happens because while packing our bags, we miss so many important things.

The baggage packing isn't a big job but many people see it as a messy job. I'll advise you to always pack your bags according to your trip. The baggage should be different according to the duration(持续时间)of your trip. You shouldn't carry unnecessary things or more than what you need.

If you're going on a business trip of not more than 2- 3 days, then make sure you don't carry more than a single bag. Pack 2—3 business suits, a night suit and also some casual(非正式的)clothes. You'll need casual clothes because you might get a chance to explore the place.

While on holidays of 5—6 days, you have to be very smart while packing your bag. First of all, check the climate of the place. If it's summer, then carry lightweight clothes and if it's winter, then you have to pack a sweater. For holidays, pack all the small things you'll be requiring. But don't carry too many things.

If you're going to a relative's place, then you can be a bit relaxed because if you miss something, you won't have to worry as your relative will be there to help you. But don't forget to buy gifts for your relatives. If the gifts are fragile, then pack them in a hard box and always keep them in between clothes. No need to carry too many clothes as you can wash your clothes at their place. This will also help you to shop more and more.