Mosquitoes can smell their dinner from an impressive distance of up to 50 meters. This isn't good news for people who give off large quantities of carbon dioxide. Any type of carbon dioxide is attractive. And larger people tend to give off more carbon dioxide, which is why mosquitoes typically prefer adults to small children. Pregnant(怀孕的) women are at increased risk, as they produce a greater­than­normal amount of carbon dioxide.

　　Movement and heat also attract mosquitoes. Therefore, if you want to avoid a mosquito bite at your next outdoor dinner, find a bench rather than a spot on the volleyball team. Here's why: as you run around the volleyball court, mosquitoes sense your movement and head toward you. What's more, the heat from your sweating body draws them closer.

　　【解题导语】　本文介绍了蚊子喜欢叮咬的人群的特点。

5．According to the passage, why do the female mosquitoes bite people?

A．Because they feed on human blood.

B．Because they like the taste of human blood.

C．Because they want to produce the next generation.

D．Because they don't like the smell of people.

C　解析：细节理解题。根据文章第一段倒数第二句Female mosquitoes (males do not bite people) need human blood to develop eggs.可知母蚊子需要人血来培养下一代。

6．What does the underlined word "trigger" in Paragraph 3 mean?

A．Make something to be worse.

B．Cause something to be active.

C．Cause damage to something.

D．Get back the use of something.

B　解析：词义猜测题。根据画线词后面的attracting them to land on unsuspecting victims可推出，画线词意为"触发，激发"。

7．According to the passage, who is more likely to attract mosquitoes?

A．A boy sleeping on the couch.

B．A man with type A blood.

C．A girl with normal levels of steroids.

D．A woman who is going to give birth to a baby.

D　解析：细节理解题。根据文章大意及第四段最后一句Pregnant(怀孕的) women are at increased risk, as they produce a greater­than­normal amount of carbon dioxide.可知，孕妇更有可能吸引蚊子。

8．What is the author's purpose of writing this passage?

A．To teach some ways to avoid mosquitoes' bites.

B．To warn people not to have dinner outside.