关于倒年系数法的理解与应用说法正确的有（）

A.折旧系数是等差数列，但折旧额不一定

B.按年序折旧系数与折旧额都是等差数列

C.折旧额是等差数列，但折旧系数不一定

D.折旧额总和等于原设备购入价减去残值

Speaker A: Good afternoon, I’m here for my four o’clock appointment with Dr. Brown.
Speaker B: ().

A. Nice to see you. I’m Dr. Brown’s secretary.

B. Why don’t you have a seat for a moment

C. Excuse me, when did you make this appointment with him

D. I’m sorry. He will be busy the whole afternoon.