题目内容：

Believe it or not, the size of the human brain has become smaller over the past 20,000 years. Scientists argue over whether this means we are becoming more or less intelligent as a species.

“I’d call that a major downsizing in an evolutionary eye blink (眨眼),” John Hawks told Discover magazine.

Why is the brain becoming smaller?

There are different theories to explain it. One is that tens of thousands of years ago, before the decline began, to survive in cold and dangerous conditions, humans needed a stronger and larger body and therefore, a larger head. Also they had to chew the tough meat of rabbits, foxes and horses. As conditions improved, the brain stopped growing, according to supporters of this theory.

Another theory comes from a recent study by David Geary and Drew Bailey. They found that brain size decreased as population density(密度) increased.

“As complex societies appeared, the brain became smaller because people did not have to be as smart to stay alive.” Geary told AFP.

But smaller brain size does not necessarily mean that modern humans are less smart than their ancestors. “Modern humans simply developed different, more complex forms of intelligence,” said Brian Hare.

Hare’s studies focus on two types of great apes: chimpanzees and bonobos. Both are much like humans, but are physically quite different from one another. The bonobo has a smaller brain than the chimpanzee, and is also much less aggressive and more tolerant.

“When it comes to working out a problem,” Hare said, “chimpanzees are much less likely to accomplish it if it involves working together. Not so with bonobos.”

The smaller brain in modern humans may be evidence that we can cooperate,” Hare told the US National Public Radio.

1.Which of the following words can be used to replace the underlined word in Paragraph 2?

A. speed    B. increase

C. decline    D. change

2.We can learn from the passage that ____________.

A. the size of human brain has something to do with many factors

B. the brain size increases because of the increase of population density

C. the abilities of the bonobos and the chimpanzees are almost the same

D. modern humans can certainly do teamwork better than other species

3.According to Brian Hare, _____________.

A. bonobos are much likely to cooperate better than chimpanzees

B. chimpanzees tend to work well with others

C. modern humans are less smart their ancestors

D. small brains are certainly connected with intelligent beings

4.Which of following is probably the best title of the passage?

A. Bonobo or Chimpanzee—Which Smarter?

B. Smaller Brain--Less Intelligent?

C. Human and Animal—More Intelligent?

D. Human Brain-Why Downsizing?