— I called you yesterday evening, but you were not in .

— Sorry, I ________ in the shop with my mother.

A．am

B．will be

C．was

D．have been

关于RC55X，说法错误的是（）.

A、RC551E系列上行均为双光口

B、RC551E系列目前还不能与PTN配合实现“零配置”

C、RC552-FE上联1光口，下联1电口，电口支持10/100M自适应

D、RC552-GE-S1（D版）上行2个千兆光口下行1个千兆电口