阅读理解天地。    

       船夫的驾驶技术特别好。行船的速度极快，来往船只很多，他操纵自如，毫不手忙脚乱。不管怎么拥挤，他总能左拐右拐地挤过去。遇到极窄的地方，他总能平稳地穿过，而且速度非常快，还能作急转弯。两边的建筑飞一般地往后倒退，我们的眼睛忙极了，不知看哪一处好。 

1．用下面的词语造句。

     不管……总……                                                                                                                           

2．解释下面的词语。 

     手忙脚乱：                                                                                                                                   

     操纵自如：                                                                                                                                    

3．用“∥”把这段话分成两层。 

4．这段话主要写                                                                                                                             。  

5．作者是从哪些方面围绕主要意思写的？

     (1)                                                                                                                                               

     (2)                                                                                                                                               

     (3)                                                                                                                                               

喷油泵的速度特性是指喷油泵每一循环的供油量随发动机转速的变化关系，即（）。

A.转速升高，供油量增加，使转速再升高，如此循环

B.转速升高，供油量减少，使转速降低，如此循环

C.转速升高，供油量不变，转速到一定值稳定

D.转速升高，供油量增加，转速升到一定值稳定