题目

已知、是非零向量且满足(－2) ⊥，(－2) ⊥，则与的夹角是      （      ）        (A).      (B)       (C).       (D). 答案：由已知得：(－2)=0，(－2) =0；即得：==2，∴cos<，>=，∴选B---Did Jim ride his bike to school this morning ?---He __________ come to school by bike. He hasn't found his bike yet.A. may B. mustn't C. can't D. can