采用钻爆法施工，一般开挖隧洞，独头推进长度不能超过( )。A_爱下问搜题

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问题单项选择题

采用钻爆法施工，一般开挖隧洞，独头推进长度不能超过( )。

A．0.5 km
B．1.0 km
C．1.5 km
D．2.0 km

答案

参考答案：D

阅读理解

Teeth are important. Strong, healthy teeth help you chew all kinds of foods that help you grow. They help you speak
clearly. And yes, they help you look your best. Here are some tips for you to take care of your teeth.

Brush your teeth in the right way.
Brush your teeth at least twice a day-after breakfast and before bedtime. If you can, brush after lunch or after sweet
snacks, too. Brush all of your teeth along the sides and back of your mouth. Spend time brushing teeth along the sides
and back of your mouth. Spend at least three minutes each time you brush. Play a song you like to help pass the time.
Get a new toothbrush every three months. When you buy a toothbrush, be sure it has soft bristles.

Learn how to floss (用牙线刷牙)your teeth.
Floss is a very important way to keep your teeth healthy. Food may hide between two teeth. Flossing can help get rid
of it. You'll need to floss your teeth at least once a day.

Have good eating habits.
You need to be careful about what you eat and drink. Eating sugar is a major cause of tooth decay(蛀牙). Eat lots of
fruit and vegetables and drink water instead of soda.

1. How many times at least should we brush our teeth a day?

A. 1.
B. 2.
C. 3.
D. 4.

2. What is the major cause of tooth decay?

A. Not brushing teeth.
B. Not changing toothbrushes.
C. Eating sugar.
D. Not flossing teeth.

3. How often should we change our toothbrushes?

A. Never.
B. Three times a month.
C. Every three months.
D. Every month.

4. Which is the right way to take care of your teeth?

A. Only brush front teeth.
B. Don't brush teeth before sleeping.
C. Spend at most three minutes brushing teeth each time.
D. Eat lots of fruit and vegetables and drink water instead of soda.

单项选择题

根据寡头垄断市场的条件，下列哪个行业最接近寡头垄断行业：（）

A.自行车行业

B.玉米行业

C.电力行业

D.石油行业