文书是以（）的凭证性工具。

根据短文，判断正(T)误(F)。

    One day a poor man was cutting a big piece of wood (木头) near a river. Suddenly his old axe (斧子) fell into

the water. He felt very sad because he lost his only axe. Then all at once a beautiful fairy (仙女) came out and

asked the man what was the matter. 

    "I have lost my axe." he said, "It fell into the water when I was cutting the wood." 

    The fairy showed him a gold axe and asked, "Is that yours?" 

    "No." said the man.

    The fairy then showed him a silver (银) axe and asked again, "Is this yours?" 

    "No." again answered the man.

    Then she showed him the old axe. 

    "Yes, that is mine." called out the happy man. 

    "I know it well enough." said the fairy, "I only wanted to see if you would tell me the truth, and now I'll give

you the gold axe and the silver axe besides (包括) your own one."

( ) 1. The man was poor, he had nothing but an old axe.

(     ) 2. The old axe fell into the river when the man was cutting the wood.

( ) 3. The fairy asked the man if he lost a gold axe, then the man said "No".

(     ) 4. When he saw his own axe, the man was very happy.

(     ) 5. At last, the man had two axes.

线上作业人员下道避车有何要求？

典型I型系统的超调量比典型II型系统（），抗扰动性能比典型II型系统（）。

引起肺炎的病原体主要是（）.

A.细菌

B.病毒

C.支原体

D.真菌

E.立克次体

遥信信号输入回路中常用（）作为隔离电路。

A、变压器；

B、继电器；

C、运算放大器；

D、光电耦合器。