多选题 It used to be widely believed that effective rewards, at least in the early stages, had to be directly related to such basic physiological ______ as thirst and hunger.

多选题 The watchman remained at his ______ all night.

多选题 The trapped miners were ______ when they heard the shouts of their friends.

多选题 The road outside the school is a ______ to the children’s safety.

多选题 It is my ______ that you didn’t try hard enough.

多选题 What you said at the conference was ______.

多选题 Barack Obama’s victory in the American presidential election was ______.

多选题 Don’t bother your boss with such ______ matters.

多选题 Despite the failure of his early experiments, the scientist ______ in his research.