While is being exerted constantly, is not always being accomplished.

1. work, force
2. force, work
3. gravity, force
4. force, gravity

The correct answer is "work and force".

Explanation:

The expression for the work done is as follows;

W=Fs

Here, F is the applied force and s is the displacement.

The work is said to be done when the force is applied on the object and there is some displacement. The work done can be positive, negative and zero.

Suppose, a man is pushing the wall. He is constantly applying the force on the wall but the wall is not moved. In this case, the work done is zero as there is no displacement.

Therefore, while force is being exerted constantly, work is not always being accomplished.

a.

explanation:

diagram is missing, but i will try to explain your doubt.

answer:

amplitude is the maximum displacement or distance moved on a point of a vibrating body or wave measured from its equilibrium position.it is equal to half the length of vibration path.