Final answer:
Weight is related to the gravitational force exerted on an object, and it is directly proportional to the object's mass.
Step-by-step explanation:
Weight is related to the gravitational force, not mass and acceleration due to gravity, atmospheric pressure, or the astronaut's fitness level.
Weight refers to the force that gravity exerts on an object, and it is directly proportional to the mass of the object. The weight of an object changes as the force of gravity changes, but its mass remains constant. Therefore, the correct answer is A) Gravitational Force.