Why did humans evolve to walk upright? Perhaps because it's just plain easier. Make that "energetically less costly", scientifically speaking. Bipedalism--walking on two feet, is one of the defining characteristics of being humans, and scientists have debated for years how it came about. In the latest attempt to find an explanation, researchers trained five chimps to walk on a treadmill while wearing masks that allowed measurement of their oxygen consumption. The chimps were measured both while walking upright and while moving on their legs and knuckles .That measurement of the energy needed to move around was compared with similar tests on humans and the results are published in this week's online edition of "Proceedings of the National Academy of Sciences". It turns out that humans walking on two legs use only one-quarter of the energy that chimps use while knucklewalking on four limbs .And the chimps, on average, use as much energy using two legs as they did when they used all four limbs. However, there were differences among chimps in how much energy they used, and this difference corresponded to their different manner of walking and anatomy .One of the chimps used less energy on two legs, one used about the same and the others used more, said David Raichlen, assistant professor of anthropology at the University of Arizona. "What we were surprised at was the variation ", he said in a telephone interview. Interview. "That was pretty exciting, because when you talk about how evolution works, variation is the bottom line, without variation there is no evolution." Walking on two legs freed our arms, opening the door to drive the world, said Raichlen. "We think about the evolution of _ as one of first events that led hominids down the path to being humans." The research was supported by the National Science Foundation and the L.S.B.Leakey Foundation. We can infer from the passage that _ . A) scientists have no idea on how humans' walking on two legs came about B) scientists have had different views on why chimps walk on four legs C) scientists have had different views on how humans' walking on two legs vame about D) scientists have had similar views on how humans' walking on two legs came about
C
One of my wonderful memories is about a Christmas gift . Unlike other gifts, it came without wrap . On September 11th ,1958,Mum gave birth to Richard. After she brought him home from hospital, she put him in my lap, saying, "I promised you a gift , and here it is." What an honor!I turned four a month earlier and none of my friends had such a baby doll of their own. I played with it day and night. I sang to it. I told it stories .I told it over and over how much I loved it! One morning, however, I found its bed empty. My doll was gone! I cried for it. Mum wept and told me that the poor little thing bad been sent to a hospital. It had a fever. For several days I Heard Mum and Dad whispering such words as "hopeless", "pitiful", and "dying", which sounded _ . Christmas was coming. "Don't expect any presents this year," Dad said, pointing at the socks I hung in the living room. "If your baby brother lives, that'll be Christmas enough." As he spoke, his eyes filled with tears. I'd never seen him cry before . The phone rang early on Christmas morning. Dad jumped out of bed to answer it. From my bedroom I heard him say, "What? He's all right?" He hung up and shouted upstairs. "The hospital said we can bring Richard home !" "Thank God !" I heard Mum cry . From the upstairs window, I watched my parents rush out to the car. I had never seen them so happy. And I was also full of joy. What a wonderful day! My baby doll would be home. I ran downstairs. My socks still hung there flat. But I knew they were not empty; they were filled with love! What is the passage mainly about ? A) A sad Christmas day B) Life with a lovely baby C) A special Christmas gift. D) Memories of a happy family
C
Q: Health officials issued a waring over common energy-saving lghtbulbs after research showed some types could potentially harm the skin and may even raise the risk of cancer. A study by the Health Protection Agency (HPA) found that some eco-friendly lightbuulbs release levels of ultraviolet (UV) radiation that are above recognized safety limits. The agency urged people who work with lamps nearby to avoid spending more than one hour within a foot of the eco-friendly bulbs. The warning was directed at those using desk lamps for long periods, such as jewellery makers, and others who might have lights close to their faces, such as car mechanics. John O'Hagan, a scientist at the HPA's centre for radiation, chemical and environmental dangers, began tests on the ligthbulbs after patient groups raised concern about them. Among the groups were patients with a skin disease called lupus, which makes people highly sensitive to light. The tests measured UV light from the lamps and found the highest levels of UV radiation, measured 2cm from the lightbulbs, were _ to being outside in direct sunlight in the summer. The most immediate risk from the lightbulbs is a reddening of the skin similar to sunburn, but there is also a small increased risk of skin cancer associated with this, again similar to that of sunburn. The risk of health problems from the lightbulbs was not so high that people should remove them from their homes. People are advised to avoid using open lightbulbs for long close work until the problem is sorted out. It has confirmed that the government will not be reviewing its strategy on introducing energy efficient lightbulbs. We can learn from the passage that _ . A) health officials issued a warning over common lightbulbs. B) jewellery makers should avoid working with the eco-friendly bulbs for more than one hour C) John O'Hagan did tests on the lightbulbs with some patients D) people are advised to avoid using open lightbulbs for long close work
A: D
Hamsters are lovely small animals which are similar to mice, and some people like to keep them as pets. They need to eat a balanced diet, or they can become very sick. That's why hamsters should be fed healthy foods. Most pet stores sell hamster mix. This is a combination of foods that are just right for hamsters. Some hamsters are picky eaters. They don't eat anything they don't like, so you have to find a hamster mix that your hamster will like. Most hamsters only eat a few tablespoons a day. You should feed them at the same time every day, or you can just keep your hamster's bowl full. Remember to clean the bowl at least once a week. Hamsters also drink a lot of water, so be sure to keep the water supply full and fresh. Just like people, hamsters like treats. Besides the hamster mix, you can sometimes feed your hamster seeds, nuts, and some other people food. You should never feed your hamster anything unless you are sure that it is safe for hamsters. Feed your hamster carefully, and always take good care of your pet! If hamsters don't have a balanced diet, they will _ . A) become sick B) drink water C) store food D) feel fresh
A