Correct Answer - C
From the property of an ellipse, we can show that `r=a` Total energy of the satellite in an elliptical orbit is,
`E=-(GMm)/(2a) :. 1/2mv_(e)^(2)-(GMm)/r=-(GMm)/(2a)`
or `1/2mv_(c)^(2)-(GMm)/a=-(GMm)/(2a)`
or `v_(c)=sqrt((GM)/a)` or `v_(c)=Rsqrt(g/a)l, (as GM=gR^(2))`