.--- I’m sorry I stepped outside for a smoke. I was very tired.. --- There is no ________ for this while you are on duty.

All that can be done ____.

In order to understand the____ of the animal, she spent many years recording its daily activities.

It can’t be a（n） _______ that four jewelry stores were robbed in one night．

Smoking, which may be _______ for some people, can cause great ______ to our health.