Energy is the ability to do work and is used in order to perform work. It is a fundamental concept in physics and is involved in various aspects of our everyday lives. Here, we will discuss the given options and explain why option D is the correct statement.

Explanation of Option A: Energy is the ability to do work and is used in order to perform work.
- Energy is defined as the capacity to do work. It is the ability to cause changes in matter or to perform tasks.
- Work, on the other hand, is the transfer of energy from one object to another. It involves the application of a force over a distance.
- Energy and work are closely related, as work is the result of the transfer of energy.

Explanation of Option B: Energy is the rate at which work is done.
- This statement is incorrect. Energy is not the rate at which work is done but rather the capacity to do work.
- The rate at which work is done is known as power, which is the amount of work done per unit of time.

Explanation of Option C: There are various units of energy, work, and energy.
- This statement is correct. Energy, work, and power have different units of measurement.
- The standard unit of energy is the joule (J), which is equivalent to the work done by a force of one newton over a distance of one meter.
- Work is also measured in joules, as it is the transfer of energy. However, other units such as foot-pounds or calories can also be used.
- Power is measured in watts (W), where one watt is equal to one joule of work done per second.

Explanation of Option D: All of the above.
- This statement is the correct option as it combines the correct explanations given in options A, B, and C.
- Energy is the ability to do work, work involves the transfer of energy, and there are various units of energy, work, and power.

In conclusion, the correct statement is option D as it encompasses the definitions and relationships between energy, work, and power.

D is the right answer