When a spacecraft travels away from earth, the gravitational force acting on it

increases

decreases

increases first and then decreases

decreases first and then increases

Gravitational force on aircraft at some distance from the Earth is given as

here we know that

= mass of Earth

= mass of aircraft

r = distance between center of earth and aircraft

now as the aircraft is flying away from the surface of Earth so here the distance between them is increasing with the motion of aircraft

So as it moves away the force between them will decrease

So here we can say that

When a spacecraft travels away from Earth, the gravitational force acting on it  

decreases

it is the second option.

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.