C is wrong because the forces on the astronaut and the craft are different
A is not true because the force is significant enough to act as centripetal force
B and D are true statements, but B is irrelevant.
As you say, g is not related to the mass of the object and is a constant.
D is the answer because as the astronaut is detached from the system, the acceleration on him increases as the mass of decreases, maintaining the same flight path
wait I remember why this answer was dodgy now (c/p from an old post)
edit:
logically, D is only true if C is also true
If gravitational force is a constant, then acceleration is inversely proportional to mass from F = ma
However they are able to orbit the earth due to gravity acting as centripetal force, and it is proportional to mass from F = Gm1m2/(r^2)
With g = Gm2/(r^2), we know that the acceleration is constant
So in fact acceleration should not change, but the force acting on the object will change get weaker, and the radius of orbit would get bigger I'm pretty sure