[单选题]
A satellite is in a low circular orbit about the Earth (i.e., it just sf4*ine-sb9/ nnmoh z(p-)v ax ki1fwm9dw1pvd+6* cj x 9 /xujiqms the surface of the Earth).qd1*9vmu w1i fx/ +c jwjx69pd What is the speed of the satellite? (The mean radius of the Earth is $6.38 \times 10^{6} \; m$.)
