The number of chairs in the room __ ten. I’m afraid a number of chairs in the room ___ lost.

A．is; is

B．is; are

C．are; is

D．are; are

驾驶员要掌握好海上天气主要应靠：（）

A.认真读书、弄清基本概念、理论和方法

B.不断实践、总结经验和长期积累

C.A或B都正确

D.A、B缺一不可