his telephone number or e-mail address, she had some difficulty getting in touch with John.
A. Not knowing
B. Not to know
C. Not known
D. Not having known
网友回答
(答案→)A. Not knowing
B. Not to know
C. Not known
D. Not having known
解析：本题考查非谓语动词。Not knowing…为现在分词的否定形式，在句中作原因状语，含伴随状况，相当于Because she didn't know his telephone number。