Do you like walking in nature? How do you feel when you hear birdsong? Happy or nervous? Recently, a study showed that hearing different sounds of bird singing may help increase(增加) our happiness.
Researchers at California Polytechnic State University（Cal Poly）did a study. They studied the effects( 作 用 ) of birdsong on people walking through a park in the US state of Colorado. Danielle Ferraro led the Cal Poly study.
Ferraro said there could be an evolutionary(进化的) reason why we like birdsong so much. “The idea is that when we hear birdsong, it could mean that we are in a safe environment,” she said. There could be many other reasons too. Ferraro said that in some areas birdsong could also mean the arrival of spring and nice weather. “Bird diversity(多样性) could also mean a healthy environment,” she added.
Ferraro and her team played recorded songs from a group of different kinds of birds. They did this in a park in Boulder, Colorado. Over several weeks, the researchers played recorded birdsong at certain times of the day and other times they did not. Then they talked with hikers(徒步旅行者) after they passed by. People who heard the recorded birdsong reported a greater sense of happiness than those who heard simply the natural birds. The researchers said that both the bird sounds and bird diversity could increase feelings of happiness.
The research team did the study during the summer. Ferraro explained why this was important. “The spring is most birds’ breeding(繁殖) season. We didn’t want to disturb(打扰) the birds too much.”
()31. Who did Danielle Ferraro's team study on?
A. The unhappy people.
B. Ferraro and her team.
C. The people walking through a park.
D. The people living near a park.
()32. Why didn't Danielle Ferraro's team do their research in spring?
A. Because they liked summer better.
B. Because they didn't want to disturb the bird breeding.
C. Because there are more birds in summer.
D. Because the birds don't like singing in spring.
()33. What can we learn from Paragraph 3?
①Birdsong can make humans feel safe
②People’s love for birdsong is important.
③Birds are active in the spring and nice weather.
④Birds like to live in a natural and healthy environment.
A. ①②③ B. ①③④ C. ②③④ D. ①②④
()34. What’s the purpose of the fourth paragraph?
A. To talk to readers about Ferraro’s study.
B. To make people close to nature.
C. To make readers understand what a study is like.
D. To show why birdsong increases people’s feelings of happiness.
()35. What is the best title for the passage?
A. Spending time in nature.
B. Birdsong makes a happy life.
C. Interesting facts about birdsong.
D. Doing the research in the right season.

31. C 32. B 33. B 34. A 35. B