-I’m sorry I stepped outside for a smoke. I was very tired.-- There is no for this

问题补充：

---- 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

答案：

A. reason

(答案→)B. excuse

C. cause

D. explanation

解析：根据第一个人的说法，他把“累”作为出去吸烟的“理由”，但下文指出“值班时间不应该擅离岗位”，在此情景中，任何“理由”或“解释”都该理解成“借口”，因此excuse最合适。