Fact 1: Plants detect and respond to the daily cycle of light and darkness. Fact 2: Circadian rhythms People and animals are usually adapted for a daily cycle of light and dark. Given the two facts above, what do plants detect because of their circadian rhythm?

Available choices:
A). Temperature changing.
B). Life and death.
C). heat produced.
D). Soil and rocks.
E). Light and dark.
F). flow of electrons.
G). Chemical energy.
H). Rain and dryness.
Answer:
E).