Parents often ask their children their Internet friends because they may be in danger.A.

问题补充：

Parents often ask their children their Internet friends because they may be in danger.

A. to meet

B. to not meet

C. meeting

D. not to meet

答案：

A. to meet

B. to not meet

C. meeting

(答案→)D. not to meet

解析：句意：父母经常要求孩子们不要见网友，因为网友可能危险。ask sb to do sth要求某人做某事，否定形式ask sb not to do sth 要求某人不要做某事，即动词不定式的否定形式，故选D.