how to do the homework I went to ask my teacher for help.A. Not to knowB. Not knowing 　C

问题补充：

how to do the homework, I went to ask my teacher for help.

A. Not to know

B. Not knowing

C. Knowing not

D. Not known

答案：

A. Not to know

(答案→)B. Not knowing

C. Knowing not

D. Not known

解析：考查非谓语动词。分词的否定式应在其前面加not,主语I 与动词know 之间是主动关系，所以用现在分词。故选B。