The houseplants in a windowless room with only fluorescent lights ...

[xclash]

The houseplants in a windowless room with only fluorescent lights begin to grow tall and leggy. Which of the following treatments would promote more normal growth?
A) Leave the lights on at night as well as during the day.
B) Add additional fluorescent tubes to increase the light output.
C) Add some incandescent bulbs to increase the amount of red light.
D) Set a timer to turn on the lights for 5 minutes during the night.
E) Turn off the lights for 5 minutes during the day.

[clippers!]

I chose C and got the answer, hope that helps.