He _______ have completed his work；otherwise, he wouldn’t be enjoying himself by the seaside.

A．should

B．must

C．wouldn’t

D．can’t

质量和初温相同的铜球和水，它们吸收相同的热量后，将铜球立即投入水中，则：[ ]

A．铜球和水之间无法热传递

B．温度由铜球传给水

C．内能铜球传给水

D．热量由水传给铜球