Sunshine does make people happier. Imagine how cheerful you are when it clears up after long cold rainy days. Let’s discover science behind sunlight.

Sunlight causes you to produce a chemical (化学物质) called serotonin (血清素). When you are exposed to sunlight, your body will make more serotonin. Higher levels of serotonin will keep you in good spirits. At night, when there is little or no light, your body produces another chemical-melatonin (褪黑激素). It helps your body relax and will make you feel tired, which can prepare you for a good night’s sleep. You should keep a good balance between these two chemicals.

However, for many people, it is hard to balance sunlight with darkness. People who stay indoors a lot may not get enough sunlight. The light in a house is usually about 100 times less than that outside on a sunny day. That’s why it is believed that those people should get outside in the sunshine. They can get some exercise, enjoy the fresh air and be happy, all at the same time.

There are places where it gets dark for a long time in the winter. People in those places are easier to get seasonal affective disorder (SAD). People with SAD usually go through bad experiences such as low energy and sadness. The most common treatment for those people is to sit under bright artificial (人工的) lights for some time.

The roles that sunshine plays in people’s life are more than those above. For example, your body produces Vitamin D (维生素D) from sunlight, which is important for being healthy. In fact, there is more science about sunlight for you to discover. So next time, when you notice the sunshine on your shoulder, take a moment to think, “Why do we love sunshine?”

1.1．Which of the following can take the place of “are exposed to” in the text?

A stay in

B care about

C dream of

D depend on

解析：选A。A.词义猜测题。原文 “are exposed to sunlight” 意为 “接触阳光”。选项 A “stay in”（处于…… 环境中）代入后 “stay in sunlight” 符合 “接触阳光” 的语境；B “care about”（关心）、C “dream of”（梦想）、D “depend on”（依赖）均与原意无关，故选 A。

2.2．What does Paragraph 2 mainly talk about?

A What can help people to keep in good spirits

B How light influences people through chemicals.

C Why melatonin can help people relax for a sleep.

D Which chemical is thought to be more important.

解析：选B。B.段落大意题。第二段核心围绕 “光线如何通过化学物质影响人” 展开，分别介绍了阳光触发血清素（愉悦）、黑暗触发褪黑激素（睡眠）的作用。A、C 仅涉及段落部分细节，D 未提及 “哪种化学物质更重要”，均非主旨，故选 B。

3.3．Which of the following is an opinion (观点) according to the text?

A There are places where it gets dark for a long time in the winter.

B People who stay indoors a lot should get outside in the sunshine.

C The light in a house is usually less than that outside on a sunny day.

D People’s bodies produce something called Vitamin D from sunlight.

解析：选B。B.观点态度题。事实是客观存在的陈述，观点是主观判断或建议。A、C、D 均为可验证的客观事实；B “长期待在室内的人应该去户外晒太阳” 是作者基于前文事实给出的建议，属于主观观点，故选 B。

4.4．Jack is a person with SAD. How could he solve his problem according to the text?

A By staying indoors a lot.

B By taking in more fresh air.

C By doing some exercise.

D By using man-made lights

解析：选D。D.细节理解题。原文明确提到 “季节性情感障碍（SAD）最常见的治疗方法是在明亮的人工灯光下待一段时间”，“人工灯光” 即 “man-made lights”。A、B、C 均未在文中提及是 SAD 的解决方案，故选 D。

5.5．Why is the sentence “Why do we love sunshine?” written in the last paragraph?

A To encourage readers to learn more about sunlight.

B To advise readers to stay in houses for enough time.

C To expect readers to realize the importance of Vitamin

D To invite readers to walk into nature to enjoy the fresh air.

解析：选A。A.句意理解题。前文提到 “关于阳光还有更多科学知识等待发现”，结尾问句 “我们为什么爱阳光？” 是为了引发读者思考，鼓励其进一步探索阳光的相关知识。B 与文意相悖，C 未聚焦 “维生素 D”，D 偏离 “探索科学” 的核心，故选 A。