If all the forces of an object cancel, the object will ___.

keep the same inertia

Imagine two people in a tug-of-war. If both sides are balanced, then this means that the flag in the middle won't move. This idea applies to any object in which multiple forces are applied to it. If the forces cancel out, then the object will stay at rest if it's already at rest. If the object is in motion, then it will stay in motion. This is Newton's First Law of Motion. It describes inertia of an object, which is the tendency of it to speed up or slow down (more or less).

a:

by the combination of an unlimited number of elements