根据所给图片完成短文。

     One day, Mr. Li was    1     a book in his office after school when a ball broke the window

and flew in.. The ball    2     him on the head. So he took the ball and came downstairs to see

who threw the ball .He met a boy at the doorway and the boy said that he threw it just now.

The boy said     3    to Mr. Li and Mr. Li praised the boy for his honesty. At last Mr. Li told

the boy to be more careful next time. The boy    4     him and said goodbye to him, running

away    5     the ball.

1._____ 2._____ 3._____ 4._____ 5._____ 

石油化工企业液化石油气缓冲罐与灌瓶间的距离，不应小于（）m。

A、5

B、10

C、15

D、20