问题
选择题
I am really sorry that I can't visit you because I have to help my sister _______.[ ]
A. learning math
B. learns math
C. for learning math
D. with learning math
答案
答案：D
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I am really sorry that I can't visit you because I have to help my sister _______.[ ]
A. learning math
B. learns math
C. for learning math
D. with learning math
答案：D