引起大气水平运动的直接原因是

A．高空和地面之间气温的差异　

B．高低空之间气压差的存在

C．同一水平面上存在气压差异　　

D．高低纬度之间的热量差异

—Are you angry?  

—Yes. He should at least answer when ____. [ ]

A. speaking

B. spoken to

C. spoken

D. speaking to