Which of the following is true about work?

A. Work depends on time.
B. Work helps retain the state of matter.
C. The SI unit of work is the watt.
D. Work can cause a change in the form of matter.

I know it is not a or b so whats the answer

You're right. It isn't a or b. The SI unit for work is the joule. So ......

To determine the correct answer among the given options, we can analyze each statement:

A. Work depends on time: This statement is indeed true. Work is defined as the transfer of energy that occurs when an object is moved along the direction of a force applied to it. It involves both force and displacement, which occur over a certain period of time.

B. Work helps retain the state of matter: This statement is not true. The concept of work is related to the transfer of energy and the application of force, not the retention of a certain state of matter.

C. The SI unit of work is the watt: This statement is not true. The SI (International System of Units) unit of work is actually the Joule (J), not the watt (W). The watt is the SI unit of power.

D. Work can cause a change in the form of matter: This statement is also true. When work is done on an object, it can indeed cause a change in the form of matter. For example, work can be done to compress a gas, apply a force to shape a material, or transfer energy to change the state of matter (from solid to liquid, for instance).

Therefore, based on the analysis, the correct answer is D. Work can cause a change in the form of matter.