题目

正方体的棱长为2，则异面直线与AC所成的角为_______. 答案：【答案】90°【解析】由BD∥B1D1，AC⊥BD，能求出异面直线B1D1与AC所成角大小．在正方体ABCD﹣A1B1C1D1中，∵BD∥B1D1，AC⊥BD，∴异面直线B1D1与AC所成角大小是90°．故答案为90°． The girl got into _____ panic when she heard ______ frightening news. A. a; the                 B. a; a                         C. the; the                   D. the; a