Read the following text. Then, answer the question that follows. Both fluorescent and regular incandescent light bulbs are safe and give off bright light. Many people like regular bulbs because they find that the light is easier on their eyes. Regular bulbs are also cheaper than fluorescent ones. On the other hand, fluorescent bulbs use less electricity and last much longer.

Which of the following details could be added to the passage without changing the single controlling impression?

a I know someone who has fluorescent bulbs in every room of her house.
b We must save the environment by using fluorescent bulbs!
c Few people realize the number of light bulbs in the average house.
d Regular incandescent bulbs are easier to find in most stores.