问题
选择题
—A medical team was sent to Japan by air five hours ago.
—So they ______________ have arrived by now. The flight usually takes four hours or so.
A．might
B．could
C．must
D．need
答案
答案：C
考察情态动词表示推测。Must have done表示对过去发生事情的肯定推测。结合句意可知本题是对过去发生事情的肯定推测。句意：—一支医疗小分队五天前飞去了日本。—那么到现在他们肯定已经到了日本了。