题目内容：

    An article published in the prestigious (有威望的) scientific journal Nature sheds new light on an important, but up-to-now little appreciated, aspect of human evolution. In this article Professors Dennis Bramble and Daniel Lieberman suggest that being able to run was the necessary condition for the development of our species which enabled us to come down from the trees. This challenges traditional scientific thinking, which claims that the distinctive, upright body form of modern humans has come about as a result of the ability to walk, and that running is simply a by-product of walking. Furthermore, humans have usually been regarded as poor runners compared to such animals as dogs, horses or deer. However, this is only true if we consider running at high speed, especially over short distances. But when it comes to long-distance running, humans do astonishingly well. They can keep a steady pace for many kilometres, and their overall speed is at least the same as that of horses or dogs.

Bramble and Lieberman examined 26 physical features found in humans. One of the most interesting of these is the nuchal ligament(项韧带). When we run, this ligament prevents our head from moving back and forth or from side to side. Therefore, we are able to run with steady heads held high. The nuchal ligament is not found in any other surviving primates, such as apes and monkeys. Then there are our Achilles tendons (跟腱) at the backs of our legs, which connect our calf (小腿肚) muscles to our heel bones — and which have nothing to do with walking. When we run, these tendons behave like springs, helping to push us forward. Furthermore, we have low, wide shoulders virtually disconnected from our skulls(颅骨), a physical development which allows us to run more efficiently.

But what evolutionary advantage is gained from being good long-distance runners? Perhaps it permitted early humans to obtain food more effectively. "What these features and facts appear to be telling us is that running evolved in order for our direct ancestors to compete with other meat-eating animals for access to the protein needed to grow the big brains that we enjoy today," says Lieberman. Some scientists put forward the theory that early humans chased animals for great distances in order to exhaust them before killing them.

"Research on the history of humans' ability to move has traditionally been controversial," says Lieberman. "At the very least, I believe this theory will motivate many researchers to reevaluate and further investigate how humans learned to run and walk and why we are built the way we are. "

1.In paragraph 1, what do the two professors suggest about humans' ability to run?

A.It is an evolutionary by-product of walking.

B.It helps to form people's ability to climb trees.

C.It has played an important role in human evolution.

D.It has not been adequately studied by scientists before.

2.What is true about the physical characteristics examined by the professors?

A.Achilles tendons assist people to walk long distances.

B.The human skull helps people to run more efficiently.

C.people's shoulders allow them to look from side to side.

D.The nuchal ligament enables people to hold their head steady.

3.According to paragraph 3, scientists believe that early humans_________.

A.always came across dangerous situations in life

B.ran after animals for long distances when hunting

C.often failed to find food because they couldn't run fast

D.developed their hunting skills by running long distances

4.Professor Lieberman thinks the new theory will _________.

A.completely explain how running developed

B.revolutionize the theory of human evolution

C.encourage more in-depth studies on the topic

D.be widely supported within the scientific community