The first one. You can’t split it into two complete sentences that make sense, only one does: “The museum is the Museum of Children’s Art.” “Which occupies a big, old house” doesn’t make sense as a sentence and is a dependent clause, therefore it is a complex sentence.
I think its B, but I might be wrong, so just check for sure. There's MLA citation websites online, you might be able to check it there. Hope this helps
I geuss its an adjective if I'm wrong plz tell me and ill fix it
The overwhelming number of geese at the park has become unacceptable