A:CH3CH2COCH2CH3
B:CH3COCH2CH3
C:CH3CH2COOCH3
D:CH3OOCH
(Ⅰ)证明:BC1∥平面A1CD;
(Ⅱ)设AA1=AC=CB=2,AB=2 2 ,求异面直线BC1与A1D所成角的大小.
组织学生阅读教材第41页插图故事“她改掉了睡懒觉的习惯”:这个女学生以前改不了睡懒觉的坏习惯,有哪些原因?为什么她后来改正了?
欧洲西部拥有世界上面积最小的国家是( )
Because he thinks it is good for her ____ (spend) more time with her friends.