With what velocity should a particle be projected so that its height becomes equal to radius of earth -

Question

( A ) $(\frac{2 GM}{R})^{\frac{1}{2}}$
( B ) $(\frac{8 GM}{R})^{\frac{1}{2}}$
( C ) $(\frac{4 GM}{R})^{\frac{1}{2}}$
( D ) $(\frac{GM}{R})^{\frac{1}{2}}$