题目

. The reason why I have to go is _____ if I don’t.    A. that she will be disappointed          B. because she will be disappointed    C. because of her being disappointed       D. that she will be disappointing 答案：A 若z＝sin－＋(cos－)i是纯虚数，则tan(－)的值为 [　　] A．－7 B． C．7 D．－7或