The correct answer is actually D, “estar dando” could be replaced by a sole “dar”, using only one verb instead of an useless one, classified as “gerúndio”.
<em>Oooh. It might have been a bad idea to leave right in the middle of that time though. Why is your teacher saying that? I don't think teachers are allowed to use that word unless it is in the text of an article you read. Maybe next time don't leave in the middle of class? </em>