Question

what has to happen for one object to orbit another object?
inertia must be greater than gravity.
gravity must be greater than inertia.
inertia and gravity must be balanced.

Explanation:

When an object orbits another, the centripetal force (provided by gravity) and the object's inertia (tendency to move in a straight line) must be balanced. If gravity were greater, the object would spiral in; if inertia were greater, it would fly off.

Answer:

Inertia and gravity must be balanced.