This question asks you what power is.
Your answer would be B) Power is the rate at which work is done
Power is not the amount of work that is being placed, but is a rate that could be measured.
For example, when you use more power, you would get things done more quickly. When you use less power, you get things done less quickly.
A visual example of the rate of power is charging an electric car. The more power you use to charge the car, the more quicker the car gets charged.
People mistakenly get mixed up with answer choice A, due to the fact that they see the word "rate", but the rest of the statement is false.
Therefore, answer choice B) Power is the rate at which work is done would be the correct answer.