—I'm sorry, but there's no smoking room in this section on the train.

—Oh, I _____ that, and I won't smoke again.   [ ]

A. don't know        

B. won't know      

C. didn't know      

D. haven't known

供用电合同的分类有（）委托转供用电合同；居民供用电合同；非标准格式合同等六大类。

A.高压供用电合同

B.临时供用电合同

C.商业供用电合同

D.低压供用电合同