Diets have changed in China — and so too has its top crop. Since 2011, the country     1    （grow）more corn than rice. Corn production has jumped nearly 125 percent over     2     past 25 years, while rice has increased only 7 percent.

A taste for meat is     3     (actual) behind the change: An important part of its corn is used to feed chickens, pigs, and cattle. Another reason for corn's rise: The government encourages farmers to grow corn instead of rice     4     (improve) water quality. Corn uses less water     5     rice and creates less fertilizer(化肥) runoff. This switch has decreased     6     (pollute) in the country's major lakes and reservoirs and made drinking water safer for people.

According to the World Bank, China accounts for about 30 percent of total     7     (globe)fertilizer consumption. The Chinese Ministry of Agriculture finds that between 2005—when the government     8     (start) a soil-testing program     9     gives specific fertilizer recommendations to farmers - and 2011, fertilizer use dropped by 7.7 million tons. That prevented the emission(排放) of 51.8 million tons of carbon dioxide. China's approach to protecting its environment while     10     (feed) its citizens "offers useful lessons for agriculture and food policymakers worldwide." says the bank's Juergen Voegele.

4 . Washington, D.C. Bicycle Tours

Cherry Blossom Bike Tour in Washington, D.C.

Duration: 3 hours

This small group bike tour is a fantastic way to see a world-famous cherry trees with beautiful flowers of Washington, D.C. Your guide will provide a history lesson about the trees and the famous monuments where they blossom. Reserve your spot before availability — the cherry blossoms—disappear!

Washington Capital Monuments Bicycle Tour

Duration: 3 hours (4 miles)

Join a guided bike tour and view some of the most popular monuments in Washington, D.C. Explore the monuments and memorials on the National Mall as your guide shares unique facts and history at each stop. Guided tour includes bike, helmet, cookies and bottled water.

Capital City Bike Tour In Washington, D.C.

Duration: 3 hours

Morning or Afternoon, this bike tour is the perfect tour for D. C. newcomers and locals looking to experience Washington, D.C. in a healthy way with minimum effort. Knowledgeable guides will entertain you with the most, interesting stories about Presidents, Congress, memorials, and parks. Comfortable bikes and a smooth tour route(路线) make cycling between the sites fun and relaxing.

Washington Capital Sites at Night Bicycle Tour

Duration: 3 hours (7miles)

Join a small group bike tour for an evening of exploration in the heart of Washington, D.C. Get up close to the monuments and memorials as you bike the sites of Capitol Hill and the National Mall. Frequent stops are made for photo taking as your guide offers unique facts and history. Tour includes bike, helmet, and bottled water. All riders are equipped with reflective vests and safety lights.

5 . We may think we're a culture that gets rid of our worn technology at the first sight of something shiny and new, but a new study shows that we keep using our old devices(装置) well after they go out of style. That’s bad news for the environment — and our wallets — as these outdated devices consume much more energy than the newer ones that do the same things.

To figure out how much power these devices are using, Callie Babbitt and her colleagues at the Rochester Institute of Technology in New York tracked the environmental costs for each product throughout its life — from when its minerals are mined to when we stop using the device. This method provided a readout for how home energy use has evolved since the early 1990s. Devices were grouped by generation — Desktop computers, basic mobile phones, and box-set TVs defined 1992. Digital cameras arrived on the scene in 1997. And MP3 players, smart phones, and LCD TVs entered homes in 2002, before tablets and e-readers showed up in 2007.

As we accumulated more devices, however, we didn't throw out our old ones. "The living-room television is replaced and gets planted in the kids' room, and suddenly one day, you have a TV in every room of the house," said one researcher. The average number of electronic devices rose from four per household in 1992 to 13 in 2007. We're not just keeping these old devices — we continue to use them. According to the analysis of Babbitt's team, old desktop monitors and box TVs with cathode ray tubes are the worst devices with their energy consumption and contribution to greenhouse gas emissions（排放）more than doubling during the 1992 to 2007 window.

So what's the solution（解决方案）? The team's data only went up to 2007, but the researchers also explored what would happen if consumers replaced old products with new electronics that serve more than one function, such as a tablet for word processing and TV viewing. They found that more on-demand entertainment viewing on tablets instead of TVs and desktop computers could cut energy consumption by 44%.

6 . Color is fundamental in home design—something you’ll always have in every room. A grasp of how to manage color in your spaces is one of the first steps to creating rooms you’ll love to live in. Do you want a room that’s full of life? Professional? Or are you just looking for a place to relax after a long day?     1    , color is the key to making a room feel the way you want it to feel.

Over the years, there have been a number of different techniques to help designers approach this important point.     2    , they can get a little complex. But good news is that there’re really only three kinds of decisions you need to make about color in your home: the small ones, the medium ones, and the large ones.

    3    . They’re the little spots of color like throw pillows, mirrors and baskets that most of us use to add visual interest to our rooms. Less tiring than painting your walls and less expensive than buying a colorful sofa, small color choices bring with them the significant benefit of being easily changeable.

Medium color choices are generally furniture pieces such as sofas, dinner tables or bookshelves.     4    . They require a bigger commitment than smaller ones, and they have a more powerful effect on the feeling of a space.

The large color decisions in your rooms concern the walls, ceilings, and floors. Whether you’re looking at wallpaper or paint, the time, effort and relative expense put into it are significant.     5    .

7 . California has lost half its big trees since the 1930s, according to a study to be published Tuesday and climate change seems to be a major factor(因素).

The number of trees larger than two feet across has declined by 50 percent on more than 46, 000 square miles of California forests, the new study finds. No area was spared or unaffected, from the foggy northern coast to the Sierra Nevada Mountains to the San Gabriels above Los Angeles. In the Sierra high country, the number of big trees has fallen by more than 55 percent; in parts of southern California the decline was nearly 75 percent.

Many factors contributed to the decline, said Patrick McIntyre, an ecologist who was the lead author of the study. Woodcutters targeted big trees. Housing development pushed into the woods. Aggressive wildfire control has left California forests crowded with small trees that compete with big trees for resources(资源).

But in comparing a study of California forests done in the 1920s and 1930s with another one between 2001 and 2010, McIntyre and his colleagues documented a widespread death of big trees that was evident even in wildlands protected from woodcutting or development.

The loss of big trees was greatest in areas where trees had suffered the greatest water shortage. The researchers figured out water stress with a computer model that calculated how much water trees were getting in comparison with how much they needed, taking into account such things as rainfall, air temperature, dampness of soil, and the timing of snowmelt(融雪).

Since the 1930s, McIntyre said, the biggest factors driving up water stress in the state have been rising temperatures, which cause trees to lose more water to the air, and earlier snowmelt, which reduces the water supply available to trees during the dry season.

9 . Wildlife has been greatly threatened in the modern age. There are species(物种) that are _______ every day. The white-naped crane is a typical example. So scientists are trying their best to _______ the species from going out of existence.

Chris and Tim work at a zoo, helping endangered cranes with their _______. Emma, a female crane, has been in their _______ since she arrived in 2004.

Born at an international crane foundation, Emma was _______ by human caretakers. This led to an unexpected _______, though she had a wonderful time there. Emma had _______ taken herself as a crane and become deeply attached to humans. She _______ to live with male cranes, and even had a _______ for killing some of them, which made it ________ for her to become a mother.

________, the two zookeepers didn’t want to see the extinction(灭绝) of this precious species. With their patience and efforts, they successfully developed a ________ of artificial breeding(人工繁殖) and natural reproduction. This ________ Emma to give birth to five baby cranes.

The two keepers are proud of their productive work. But before they can be ________, more efforts must be made, because the population of the crane in the wild is on the ________, and many other species appear headed toward extinction. ________, not everyone has realized that wildlife has thoughts, feelings, and most importantly, equal rights to survive.

How can we ________ the ever-widening gap that separates us from other animals? Chris and Tim offered us the ________: human beings took it for granted that their ________ held all the solutions, but maybe their hearts can be a better ________.