—Please keep the window _____, Jack ! It’s so hot!

—Ok! And may the door be ______ now?

A．opened, close

B．open, closed

C．closed, closed

D．close, opened

下列电力系统短路故障中，无零序分量的短路是（）。

A.三相短路

B.两相短路

C.两相短路接地

D.单相接地短路