问题描述：
20.Three fifths population of this city _____________ (be) from other cities
21.I _______________ (study) English at this school for three years.
22.Do you have any problem ______________ (get) to the top of the hill?
21.I _______________ (study) English at this school for three years.
22.Do you have any problem ______________ (get) to the top of the hill?
问题解答：
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