If the question isn't actually testing you on the grammar point it's asking about, or the multiple choice answers have an answer that's too obvious for reasons unrelated to the grammar point (e.g. only the correct answer is a noun), click the ? button at the top to report a quiz problem either during the question or right after you answer. All you need to explain is that the multiple choice answers aren't related to the point being tested, and they are usually fixed pretty quickly.
If I remember correctly, this kind of weirdness happens when the grammar sentences have corrections applied, and the word selected to be missing from the sentence gets shifted.
I too would not understand what the issue is about. I've had enough grammar quizzes to know it usually isn't necessarily to fill in the blank on the grammar point itself, but simply to fill in the blank on the word which completes the sentence. Perhaps this is flawed in which this doesn't actively quiz you on the grammar, but it doesnt seem so difficult in concept to show you the sentence in which it is used. Maybe you would need a different quizzing style for that?
