8. He was so deep in thought, thinking of the problem he knocked into the tree without no

发布时间：2020-08-16 06:14:13


8. He was so deep in thought, thinking of the problem      he knocked into the tree without  noticing it.
A. when
B. while
C. because
D. That

网友回答

A. when
B. while
C. because
(答案→)D. That
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