Select the independent clause (it is a sentence). a) When my children go to visit. b) During the summer, when my children go to visit. c) During the summer in the mountains, my children. d) When my children go to visit my mother, they have fun.

 d) When my children go to visit my mother, they have fun.

Explanation:

An independent clause contains a subject and a predicate.  The subject of d) is they and the predicate is have fun.  It is the only option that has both a subject and predicate (ie. is a complete sentence). Also of note is that in d) When my children go to visit my mother is a dependent clause.

b would have to be the answer