引起皮质醇增多症的病因中应除外 （）

A.下丘脑-垂体功能紊乱致肾上腺皮质增生

B.肾上腺皮质肿瘤

C.垂体腺瘤致肾上腺皮质增生

D.继发于垂体以外肿瘤ACTH的异源性分泌

E.特发性肾上腺萎缩

--- Hello! Is Mr. John in the office?

--- Yes. But I’m sorry. He is busy _________ and can’t speak to you.

A．at once

B．at present

C．at the end

D．at first