The ability to move or change an object or what a wave carries

The ability to move or change an object or what a wave carries is called Energy

Explanation: Waves are disturbances in physical quantities. Example of waves are light waves, sound waves, or transverse oscillations of a string. These disturbances use energy to create and propagate, for it to move the constituent particles or change the electric or magnetic fields. Therefore, power of a wave is therefore, energy transported divided by unit time caused by the oscillations of a particular wave. The derivation of a formula for the power depends on the medium -- for light waves, the power is measured by the pointing vector, whereas for oscillations on a string, the power can be computed directly by balancing forces through the application of newton law. However, for all types of waves, the formula and physical meaning of the power takes similar forms, typically depending on the square amplitude of the waves among other factors.

its c i just checked it

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.