--- Could you bring me that novel you _____________ me about when I dropped in on you?

--- Sorry, I can’t. I have given it to a friend.

A．told

B．would tell

C．had told

D．had been telling

以下有关放置像质计的说法正确的是（）

A.原则上每一张射线底片都应放置像质计

B.周向曝光技术中，在至少每隔120º的位置上放置一个像质计

C.像质计一般放在射线底片的两端，像质计最细的金属丝应靠近端头处

D.以上都对