Work in physics is calculated using the formula that relates force to the distance over which that force is applied. Specifically, work is defined as the product of the force applied to an object and the distance over which that force acts, when the force is applied in the same direction as the movement of the object.
In the case of the correct answer, Force x Distance, you can see that if a force is exerted on an object and that object moves in the direction of the force, then work is done. For example, if you push a box across the floor, the amount of work you do depends on how hard you push (the force) and how far the box moves (the distance).
When calculating work, it is also important to note that if the force is not in the direction of the movement, only the component of the force that acts in the direction of the movement contributes to the work done. However, in the context of this question, assuming a constant force and displacement in the same direction makes the direct use of the formula straightforward, leading to the conclusion that the work done is effectively the product of these two quantities.
Understanding this definition and calculation of work is foundational in physics, as it connects to various concepts, such as