A:experiences; great experience
B:experience; great experience
C:experiences; a great experience
D:experience; a great experience
在△ABC中, 已知向量AB→=COS18°,COS72°, AC→=2cos63°,2cos27°,则cos∠BAC的值为( )
你认为下列各项不能作为海陆变迁证据是的( )