质数一定不是2、3、5的倍数。
(Ⅰ)求异面直线D1E与A1D所成的角;
(Ⅱ)若二面角D1﹣EC﹣D的大小为45°,求点B到平面D1EC的距离.
下列各组词语中错别字最多的一组是( )
On May 22, a Han taxi driver an old lady to the hospital as soon as he could in Xinjiang.