C. To raise money for medical research.

D. To promote the elderly people’s welfare.

29. How has the project affected Ruth Xavier?

A. She has learned new life skills.

B. She has gained a sense of achievement.

C. She has recovered her memory.

D. She has developed a strong personality.

30. What do the underlined words “embark on” mean in paragraph 7?

A. Improve.

B. Oppose.

C. Begin.

D. Evaluate.

31. What can we learn about the project from the last two paragraphs?

A. It is well received.

B. It needs to be more creative.

D. It takes ages to see the results.

C. It is highly profitable.

D

Human speech contains more than 2,000 different sounds, from the

common “m” and “a” to the rare clicks of some southern African languages.

But why are certain sounds more common than others? A ground-breaking,

five-year study shows that diet-related changes in human bite led to new

speech sounds that are now found in half the world’s languages.

More than 30 years ago, the scholar Charles Hockett noted that speech

sounds called labiodentals, such as “f” and “v”, were more common in the

languages of societies that ate softer foods. Now a team of researchers led by

Damián Blasi at the University of Zurich, Switzerland, has found how and

why this trend arose.

They discovered that the upper and lower front teeth of ancient human

adults were aligned (对齐), making it hard to produce labiodentals, which

are formed by touching the lower lip to the upper teeth. Later, our jaws

changed to an overbite structure (结构), making it easier to produce such

sounds.

The team showed that this change in bite was connected with the

development of agriculture in the Neolithic period. Food became easier to

chew at this point. The jawbone didn’t have to do as much work and so

didn’t grow to be so large.

Analyses of a language database also confirmed that there was a global

change in the sound of world languages after the Neolithic age, with the use

of “f” and “v” increasing remarkably during the last few thousand years.