Explanation:

- When two forces act on an object from opposite directions, they cancel each other out to some extent. The remaining force is what affects the object.

- Option 1: Product

- This would mean multiplying the magnitudes of the two forces. This doesn't make sense for forces in opposition.

- Option 2: Sum

- This involves adding the forces together. For opposite forces, directions are important so this is irrelevant.

- Option 3: Ratio

- Dividing the magnitudes of the forces doesn’t help in finding net force.

- Option 4: Difference

- The net force is calculated by subtracting the smaller force from the larger one.

- Correct Answer: Difference