Every director needs an assistant that he can ______ to take care of problems that may occur in his absence.

单项选择题No sooner had I closed the door than somebody started knocking ______ it.

单项选择题If you don t put the milk in the refrigerator, it may ______.

单项选择题They built the wall especially high so that the little boy couldn t ______ it.

单项选择题Stupid people often find it difficult to ______ their prejudices.

单项选择题Do you know why John didn t ______ at the party yesterday evening