Answer:
c) nonzero, directed toward the spaceship
Explanation:
As we know that net gravitational force due to spherical shell inside all its points will always be zero
So if planet is a spherical shell then inside the planet net gravitational force is zero on the people living in it
So when massive spaceship land on the surface of planet then the gravitational force of the spaceship is experienced by the people inside the shell
So here the gravitational force on the people is nonzero and it is towards the spaceship which landed on the surface of planet