[单选题]
Two planets have thei*wmm9 wjkg3,9w 5e )2hxi r+7qxtl1yvab6kx same surface gravity, but planet B has twice the radius of planetx5hwvr +t )e 2ybak6l7x9q1x i A. If planet A has mass m, what is the mass of planet B?
A. $0.707 \; m$
B. $m$
C. $1.414 \; m$
D. $4 \; m$
