Question

according to newtons first law of motion, when will an object at rest begin to move?
when its inertia decreases to zero
when an unbalanced force acts upon it
when the action and reaction forces are equal
when two equal and opposite forces act upon it

Explanation:

Newton's first law (law of inertia) states that an object at rest stays at rest unless acted upon by a net external (unbalanced) force. Inertia is an intrinsic property that does not decrease to zero; equal and opposite forces (balanced) or equal action-reaction forces do not create a net force to change the object's state.

Answer:

when an unbalanced force acts upon it