Gravitational force of attraction on the Moon is given by
g on the Moon is found to be around 1/6th of g on the Earth. So it is around 9.81/6 m/sec²
If the net external force on a body is zero, it means the body has an acceleration of 0. It means the velocity is constant (it can be zero also). So linear momentum is a constant.over time. It can be zero also.
==> Force = rate of change in momentum. = 0. SO momentum is a constant.
COrrect answer is c) constant.