问题描述：
pay off和pay back选题
The teacher's efforts ___when one of his students was admitted to Beijing university last summer.
用pay back还是pay off?给我理由.
The teacher's efforts ___when one of his students was admitted to Beijing university last summer.
用pay back还是pay off?给我理由.
问题解答：
我来补答展开全文阅读