Young students are ______ not to smoke, either in or out of school.
He had thousands of students, many of ______ gained great success in their own field.
He asked a lot of questions, none of ______ was easy to answer.
He asked a lot of questions, and none of ______ was easy to answer.
He told me that he had two girl-friends, neither of _______ knew anything about the other.
He told me that he had two girl-friends, and neither of _______ knew anything about the other.