They always have a good time ＿＿＿＿ each other.

A．chatting

B．chat

C．chatting with

D．chat with

下列说法正确的是（N_A为阿伏加德罗常数）（）

A．124gP₄含有p—P键的个数为4N_A

B．12g石墨中含有C—C键的个数为1．5N_A

C．12g金刚石中含有C—C键的个数为2N_A

D．60gSi0₂中含Si—O键的个数为2N_A