根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。
Gone are the days when men and women couldn't associate with each other．If we want to deal with the association between boys and girls properly, here are some "dos and don'ts" for you to follow．
___71___ Our schools and classes are made up of boys and girls．It is very natural for boys and girls to contact each other and build up the friendship with the students of the other sex．Generally speaking , we should broaden the circle of the association． 72 We should have more friends of the other sex instead of one or two．We should contact the students in public instead of in secret．
Contact the students of the other sex warmly, generously and sincerely．Don't be too nervous or too shy in contact with a person of the other sex． 73 If you are too shy a
