The temperature at which the root mean square velocity of hydrogen molecules equals their escape velocity on earth is closest to {Boltzman constant = $1.38\times {10}^{-23}$ mk units radius of earth $R_e=6.4\times {10}^6 \mathrm{m},\hspace{0.17em}\hspace{0.17em}\mathrm{g}\hspace{0.17em}=10 {\mathrm{ms}}^{-2}$ }