Welcome to JavaRanch, and thanks for the feedback!
I believe the answer is correct as it stands. It says that the default clause will execute if no case matches, and that's absolutely true. It's possible that the default will execute if a case matches, also -- but that doesn't make the original statement false. If the question had said "True or false: the default clause will only execute if no case matches", then I would agree with you, but it does not say that.