---I’m sorry for losing your book. I will buy a new one for you.

---________. I have another copy.

A．Thank you

B．Happy to hear that

C．Never mind

D．Of course

一辆卡车从静止开始由山顶向山下下滑，卡车司机关闭了发动机，滑到山底速度是 4km/h，如果卡车关闭发动机以初速度3km/h由山顶滑下，则卡车滑到山底的速度是（  ）

A．

B．

C．

D．