.--- I’m sorry I stepped outside for a smoke. I was very tired..
--- There is no for this while you are on duty.
A. reason
B. excuse
C. cause
D. explanation
网友回答
A. reason
(答案→)B. excuse
C. cause
D. explanation
解析：名词辨析。A原因；B借口；C原因；D解释；句意：—对不起我要出去抽支烟。我太累了。—当你在值班的时候，不应该有这样的借口。根据句意说明B正确。