According to newton’s first law of motion, when will an object at rest begin to move? 1 when its inertia decreases to zero 2 when an unbalanced force acts upon it 3 when the action and reaction forces are equal 4 when two equal and opposite forces act upon it

Newton's first law states that:
"An object will remain at its state of rest or motion until an external force acts on it".

This means that, if the net force acting on an object at rest is zero, the object will remain at rest.
The object will start to move only when there is an unbalanced force acting on it.

Based on this, the correct choice is:
2. when an unbalanced force acts upon it