Boys and girls, you should know what a great difference good manners in public will to a

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A. owe
B. belong
C. contribute
(答案→)D. make
解析：句意:男孩和女孩们,你们应该知道礼仪将将会对一个人在公共场合造成一个很大的影响。make a great difference有意义，有差别，有影响。good manners in public will make to a person是定语从句修饰 difference ，省略了关系代词that或which，礼仪在公众场合对一个人所造成的影响。故选D。