Help?

What is 4 over Sqr.Rt of 10 - Sqr.Rt of 6?

A) Sqr.Rt of 10 + Sqr.rt of 6

B) 4

C) 4 Sqr.Rt of 10 + 4 Sqr.Rt of 6

D) 4 Sqr.Rt of 10 - 4 Sqr.Rt of 6 over 16 - 2 Sqr.Rt of 15