题目

长方体中，，则异面直线   与所成角的余弦值为 A．          B．              C．            D．         答案：D解：如图, 异面直线与所成角等于， 在中，， ，These surveys indicate that many crimes go　　　　 by the police， mainly because not all victims report them. A．to be unrecorded B．to have been unrecordedC．unrecorded D．unrecording