问题
It may be necessary to stop______in the learning process and go back to the difficult points in the lessons.
A:at intervals
B:at random
C:at ease
D:at length;
B:at random
C:at ease
D:at length;
正确答案是：
同类题型
John sold the camera yesterday which his brother him as a birthday present from Japan
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So in the darkness that he didn’t dare to move an inch.
The man should be excused becausehe caused the damage _______
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