[单选题]
A satellite is in a low circular orbit about tukmf wu :4,zke(7o+ojhe Earthyqy47*xi11sdtmg: t m (i.e., it just skims the surxt1t*m s i74qg ym:yd1face of the Earth). What is the speed of the satellite? (The mean radius of the Earth is $6.38 \times 10^{6} \; m$.)
