What happens after a thruster is fired to push a spacecraft a. the spaceship will not move due to air resistance b. the spaceship will not move because it only works on earth c. the spaceship will move and will not stop until it is stopped by an equal and opposite force d. the spaceship will move and then slowly come to a stop on its own

The thruster releases small amounts of substance (in the form of a gas or liquid) at very high speed out of the nozzle. Since Newtons  3rd law states that each action has an equal and opposite reaction, therefore spacecraft should also experience a push in the opposite direction. Therefore the spaceship will move. This will only stop when it faces an equal opposite force.

c. the spaceship will move and will not stop until it is stopped by an equal and opposite forced

second mirror gathers light from a faraway object and reflects it to another mirror. - a.