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问题: 1、Greater efforts to increase agricultural product

1、Greater efforts to increase agricultural production must be made if food shortage _____ avoided.
A is to be B is 为什么不用B,if条件句不是可以用现在时表将来吗
2、The house belongs to my aunt but she ______ here any more.
A hasn't lived B doesn't live
为什么不用A?而用B ?

解答:

1.is to be/do除了表示将来,还相当于情态动词may/can,表示可能性。这句就是后者。
2. live是个持续性动词,应该指出持续多长时间了。而这句没有。