Unit 1 Women of achievement reading课时作业

第一节 七选五 (共5小题；每小题2分，满分10分)

　　根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

　　We usually think of bacteria as being dangerous and a cause of human diseases. 1 Certain types of bacteria actually play a very important role both inside our bodies and in the environment around us.

　　Some species of bacteria do make us sick, but others may actually prevent us from getting sick. Our bodies have what doctors call a "normal flora (正常菌群)". The bacteria in our normal flora are harmless, and most of the time we don't even know that these bacteria are there. When our bodies are invaded by some dangerous bacteria, the normal flora can prevent these bacteria from hurting us. 2

　　Bacteria help us digest food and produce vitamins. The normal flora in the gut (肠道) can be helpful by breaking down food that can't be digested by our bodies. 3 Besides, some bacteria in the gut can produce small amount of B vitamins.

　　When plants and animals die, it is bacteria that break down the remains and return food to the soil. 4 Without the action of bacteria, soil would not be able to help plants grow and dead organisms would not be broken down.

　　 5 Fermentation (发酵) of milk into cheese and yogurt, for example, would not be possible without the activity of some bacteria. These bacteria are also sometimes used in making wine.

　　A．This helps us get more energy from what we eat.

　　B．However, the truth is that bacteria can also be good.

　　C．Many food production processes need the help of bacteria.　

　　D．There are more bacteria in your mouth than there are people in the world.

　　E．Some species of bacteria can be useful in agriculture and other industries.

　　F．The benefits of certain bacteria on ecological balance are attracting attention.

　　G．They do this either by crowding out the invaders or by killing the bad bacteria.

1.选B　本空前后两句之间是转折关系，B项承上启下，引出有益菌。

　　2．选G　本段讲的是我们体内的一些菌群能保护我们免受其他细菌的伤害，G项是对上句的解释说明。

3．选A　本空是对上句的进一步说明，肠道的有益菌帮助我们消化食物，这样我们