题目内容：

We have PE lessens___every Tuesday and Friday.so wehave them___ a week
A on;two times B /;twice C on;twice D /;two times

优质解答

B
名词前有every等修饰时不用介词
twice a week 一周两次 （根据星期二‘ 一次’ 和星期五‘一次’ 可知）