Answer :
B is a fragment. A fragment is any sentence that either doesn't have a subject, or that doesn't have a verb.
B has no verb. The house(which is the subject) is doing nothing.
If you wanted to correct this sentence you would get something like:
A house with no cars in the driveway usually means that no one is home.
B has no verb. The house(which is the subject) is doing nothing.
If you wanted to correct this sentence you would get something like:
A house with no cars in the driveway usually means that no one is home.