若四棱柱ABCD-A1B1C1D1的底面是边长为1的正方形,且侧棱垂直于底面,若AB1与底面ABCD成60°角,则二面角C-B1D1-C1的平面角的正切值为( )。
If you can’t English, you can it in Chinese.
A.speak, talk
B.speak, say
C.say , speak
D.talk, speak