【单选题】I have _______ much work to do _______ I have no time to go out with you. [ ]
【单选题】—Do you know where the headmaster is? I have something urgent. —Oh, he ____ have gone far, for the computer is still on in the office.
【简答题】消化管上皮,大部分为 ,但口腔、咽、食管和肛门则为 。