If a planet consits of a satellite whose mass and radius were both half that of the earth, the acceleration due to gravity at its surface would be (g on earth=`9.8m//sec^(2)`)
A. `4.9 m//sec^(2)`
B. `8.9 m//sec^(2)`
C. `19.6 m//sec^(2)`
D. `29.4 m//sec^(2)`
