---We all wonder ____ the relationship between France and China is good again now?

---Because the two countries have common national benefits.

A．why it is that

B．why it is

C．that it is why

D．it is why

在4min内通过的电阻为4Ω的导体的电量为960C，则这4min内导体产生的热量为（）。

A.15360J

B.960J

C.3840J

D.7680J