—Hey, who’s that man over there? He    us since we came in.

—The one by the door? I don’t know. He looks like a lawyer or something, not a journalist. Perhaps he      here to look round, like us.

A．has watched；only came

B．is watching；had only come

C．has been watching；has only come

D．had been watching；came

离心式压缩机制冷量调节的方法有压缩机吸入蒸气节流、（）、改变进口导叶角度、改变冷凝器的冷却水量、热气旁通。