[单选题]
Consider a small satellite movingyre1z)/9 epk e in a circular orwpm(umk hly4+6fbpl,n98v,g u5ii;f bit (radius r) about a spherical planet (mass M). Which expression gfnif l6 h uml4ki; m+b9p(wgyvp8, u,5ives this satellite's orbital velocity?
A. $v = GM/r$
B. $\sqrt{GM/r}$
C. $GM/r^2$
D. $\sqrt{GM/r^2}$
