在四面体ABCD中,E,F分别是AC与BD的中点,若CD=2AB=4,EF⊥BA,则EF

在四面体ABCD中,EF分别是ACBD的中点,若CD2AB4EFBA,则EF

CD所成的角为(  )

   A90°       B45°      C60°           D30°

答案

D

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