The spacecraft and the Moon both have mass, so there's gravitational force between them, trying to pull them together.
As the spacecraft flies toward the Moon, the distance between them decreases, so the strength of the gravitational forces INcreases (A).
Note: The Moon's gravitational pull on the spacecraft is EQUAL to the spacecraft's gravitational pull on the Moon. Gravitational forces always occur in equal, opposite pairs. Your weight on Earth is equal to the Earth's weight on you.
