
在长方体\(ABCD-A _{1} B _{1} C _{1} D _{1}\)中,\(BC=2\),\(AB=BB _{1} =4\),\(E\),\(F\)分别是\(A _{1} D _{1}\),\(CD\)的中点,则异面直线\(A _{1} F\)与\(B _{1} E\)所成角的余弦值为\((\:\:\:\:)\)
A. \( \dfrac { \sqrt {102}}{34}\)
B. \(- \dfrac { \sqrt {102}}{34}\) C. \( \dfrac { \sqrt {5}}{5}\) D. \( \dfrac { \sqrt {6}}{6}\)