The teacher          with his son.         [ ]

A. swimming                

B. are swimming        

C. is playing tennis            

D. swims

下列对于气瓶入库储存前的检查，表述正确的是( )。

A．气瓶在充装时若做好检查验收工作，入库储存前就不用再检收一遍

B．对有缺陷的气瓶，应禁止入库

C．对于储存多种气体的储存库，应按气体种类分别建立登记簿

D．对检查验收不合格的气瓶，应逐只进行登记