Answer:
I know I'm three years late so the answer might've changed, but the answer at the time of writing this is D
Explanation: Whenever we look at houses, my Dad says he doesn't want to move.
A main clause is a clause that makes sense on its own and can also exist in a sentence on its own. A Subordinate clause is a clause that does not make sense on its own and cannot be a sentence on its own. The subordinate clause explains or completes the meaning in the main class. Two main clauses are joined by and, but or or. If you want to learn more I suggest looking at major reading sites that go into more detail into the subject.
