You probably know many of the things that you can do with the hundreds of different muscles in your body. But have you ever thought about how the muscles in an animal's body are different from yours? An animal's muscles are made to do the things that are most important for its life.

    Lions are hunters. They depend on their ability to catch other animals. Lions must be fast in order to catch their prey(猎物). The powerful muscles in their back legs allow them to run at speeds of more than 30 miles per hour. They can also jump a distance of more than 35 feet. The strong muscles in their front legs help them catch their prey.

    Snakes also use their muscles for hunting prey and for movement, but their muscles work in very different ways than lions' do. Because snakes do not have any legs, they use their muscles to push against the ground or other objects to move themselves forward. Their muscles also allow them to eat things that seem much too large. For example, a snake may eat an egg that is larger than the width of its body. How does this happen? The snake's strong neck muscles work together to push the egg down the mouth.

    The elephant's long nose has a lot of muscles. Scientists believe that the nose alone has more than 100,000 muscles! This is because the elephant uses its nose much in the same way that people use their hands and fingers. Even though the nose is large, it can perform surprisingly tasks. For example, an elephant can pick up a small leaf from the ground. The nose can also be a powerful tool. An elephant can use its nose to pick up a tree by its roots or even to lift a baby elephant.

    The great muscles of these animals seem pretty unbelievable. But the muscles in your body work exactly the way you need them to. After all, it might be fun to be able to jump a distance of 30 feet, but as a human being, there is just not much need for it.

物体放到凸透镜前，到凸透镜的距离是16cm，此时光屏上得到的是缩小的像，则所用透镜的焦距可能是（  ）

    Lindsay Renwick, the mayor of Deniliquin, a country town in New South Wales, misses the constant whir（嗡嗡声）of the rice mill whose giant fans dried the rice. The Deniliquin mill, the largest rice mill in the Southern Hemisphere (南半球), once processed enough grain to meet the needs of 20 million people globally. But six years of drought have had a destructive effect, reducing Australia's rice crop by 98 percent and leading to the mothballing of the mill last December.

    Drought affects every agriculture industry based in Australia, not just rice – from sheep farming, the country's other backbone, to the cultivation of grapes for wine, the fastest-growing crop there, with that expansion often coming at the expense of rice. The drought's effect on rice has produced the greatest impact on the rest of the world, so far. It is one factor contributing to skyrocketing prices, and many scientists believe it is among the earliest signs that a warming planet is starting to affect food production.

    Researchers are looking for solutions to global rice shortages – for example, rice that blooms earlier in the day, when it is cooler, to fight against global warming. Rice plants that happen to bloom on hot days are less likely to produce grains of rice, a difficulty that is already starting to emerge in inland areas of China and other Asian countries as temperatures begin to climb. 'there will be problems very soon unless we have new varieties of rice in place,” said Reiner Wassmann, climate change director at the International Rice Research Institute (IRRI). The recent reports on climate change carried a warning that could make the news even worse: that existing models for the effects of climate change on agriculture did not yet include newer findings that global warming could reduce rainfall and make it more variable.

    Yet the effects of climate change are not uniformly bad for rice. Rising concentrations (浓度) of carbon dioxide, the main greenhouse gas, can actually help rice – although the effect reduces or disappears if the plants face unnecessary heat, inadequate water, severe pollution or other stresses. Still, the flexibility of farmers here has persuaded some climate experts that, particularly in developed countries, the effects of climate change may be relieved, if not completely avoided. “I'm not as negative as most people,” said Will Steffen, director of the Fenner School of Environment and Society at Australian National University. “Farmers are learning how to do things differently.”

    Meanwhile, changes like the use of water to grow wine grapes instead of rice carry their own costs, as the developing world is discovering. “Rice is an essential food,” said Graeme Haley, the general manager of the town of Deniliquin. “Wine is not.”