Football,-----is a very interesting game,is played all over

选C
首先必然不选D。
其次,it is a very interesting game构成了一个完整的句子,使得全句出现句中句,违背英语一个句子一个句号的基本语法,必然排除。
再次,如果用that引起同位语从句,则that前面不会有逗号,故排除。
最后,本句子的主干为Football is player all over the world,中间which句修饰football。