问题描述：
( )his telephone number, the manager had some difficulty getting in touch with the clerk.
a.Not knowing
b.Knowing not
c.Not having known
d.Having not known
这道题选哪个,选它的原因是什么,谢谢~
a.Not knowing
b.Knowing not
c.Not having known
d.Having not known
这道题选哪个,选它的原因是什么,谢谢~
问题解答：
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