汽车与路面的动摩擦因数为μ，公路某转弯处半径为R（设最大静摩擦力等于滑动摩擦力）

在人的运动系统中，骨骼肌在运动中起着[ ]

A．杠杆作用

B．支点作用

C．动力作用

D．连续作用

用括号内所给单词的适当形式填空。（5分）

Will you help ______ (clean) up the classroom?

2.  It is a ______(please) for me to stay with you.

3.  Eating too much _________(fry) food is not good for our health.

4.  They plan ______(set) up a basketball team in our school.

5.  At last they were in__________. (agree)

6.  Our teacher asks us to read some __________(educate) books in our free time.

7.  China has many fantastic sights, _________(include) the Great Wall.

8.  Yesterday we saw some _________(fisherman) fishing in the river.

9.  Beijing is one of the ___________(lively) cities in China.

10. The article ________(main) talked about teenagers’ problems.

试述消化道平滑肌的一般特性。

劳动者到劳动保障监察机构举报投诉的时限？