The Moon does not crash into the Earth because:

(a) the net force on it is zero.

(b) it is beyond the main pull of the Earth's gravity.

(c) it is being pulled by the Sun as well as by the Earth.

(d) it is freely falling but it has a high tangential velocity.

(d) it is freely falling but it has a high tangential velocity.

Explanation:

When Moon goes around the Earth it is pulled by the gravity of the Earth. Along with the gravity it also has its own velocity with which it is going around the Earth. The two factors combine together to give the desired orbit of the Moon around the Earth.

It can be considered like the Moon is trying to fall onto the Earth but the tangential velocity stops it from doing so. This was proved by Isaac Newton in an experiment generally known as Canon ball experiment. If you fire a canon with enough speed it will not land on Earth but take a complete circle of Earth and hit you back in the head. The same phenomenon applies to satellite orbiting the Earth or Earth orbiting the Sun.

(d) it is freely falling but it has a high tangential velocity.

Explanation:

The Moon does not crash into the Earth because it is freely falling but it has a high tangential velocity, that is, actually the moon is falling toward the earth, but since it's moving so fast, then it will never hit the earth. The moon is so far away from the earth and move so fast that it falls around the earth in a continuous circular path. In other words, the high tangential velocity makes the moon to move around the earth. If the moon was moving slowly, gravity would make the moon to fall into the earth.