Our math teacher is very kind he looks very serious.A. becauseB. thoughC. ifD. when

问题补充：

Our math teacher is very kind he looks very serious.

A. because

B. though

C. if

D. when

答案：

A. because

(答案→)B. though

C. if

D. when

解析：because因为；though虽然，尽管；if是否，如果；when当……时。句意：尽管他看起来很严肃，我们的数学老师很和蔼。结合语境可知选Ｂ。