题目

I failed in the final exam last term and only then the importance of study. A . I realized B . I realize C . had I realized D . did I realize 答案：D在正三棱柱ABC-A1B1C1中，若AB＝BB1，则AB1与C1B所成的角的大小为………………（　　） A.60°                B.90°            C.105°           D.75°