如图所示的是为纪念发现“磁生电”现象的物理学家 而发行的一枚邮票，该发现导致了世

I often go _____________ on Saturday.[ ]

A. swims

B. swim

C. swimming

75. He had never spent a________day. 

A．more worry

B．most worrying

C．more worrying

D．most worried

--David has been away for more than 25 days．

--I miss him very much．You know，25 days      short．            

A．is

B．isn’t

C．are

D．aren’t

食物中毒有哪些特点？

电动机的漏抗与（）成反比。

A、堵转转矩

B、最大转矩

C、堵转电流倍数