[单选题]
The acceleration of gra+ oacec /vtle;z/,n yw9t55jbvity on the Mkx*r)fzuzr ))3l 9sjnoon is one-sixth what it is on Earth. The radius of the Moon is one-fourth that of the ulfz)* 9rz 3ksjrn) )xEarth. What is the Moon's mass compared to the Earth's?
