For #4, the question is different than the others because 休み is a noun, not a verb. (Lit. Saturday, Is (your) company on vacation?) When asked this way, the answer should correspond with a noun in the answer. "Yes, (the company is) on vacation" -「はい。休みです」　 Or for the negative,　"No, (It's) not on vacation" 「いいえ。休みではありません」　Or　「いいえ。休みじゃないです。」 ("On vacation" sounds slightly awkward in English, but it just means that the company is closed/doesn't require employees to come in on that day) 休む as a verb means "to take a break/to take a day off" Think means that if the question was phrased 「明日休みますか？」 (will you take tomorrow off?) you would respond with the regular Godan indicative forms はい。休みます。 いいえ。休みません。 An easy way of spotting a noun(adjective) is by looking for "です” In #4, the question uses ですか？meaning that the thing that comes before it is a noun/adjective If a question ends in ますか？ then it is preceded by the verb's root (either Ichidan or Godan)