Answer:
The river bank can expand due to the water breaking apart which can cause sediment to move and change/erode
As we know that total work done by a force is given by


so it is product of force and displacement along same direction
as we can write it as

so it must be the product of force and displacement in same directions so correct answer must be
<u>b. is parallel to the displacement of the object</u>
Answer:
A chair at rest on the floor has two forces acting on it its own weight that pulls it downward and the floor pushing upward on the chair, both of these forces are acting on it but the net force is 0, so the chair remains at rest and its velocity stays at 0.