Interrupting the Night with a Flash of Light Can Trigger

Multiple Choice

Interrupting the night with a flash of light can trigger flowering in a long-day plant.Why doesn't introducing a short period of darkness during the day cause a short-day plant to flower?

A) Sunlight contains enough far-red light to inhibit phytochrome induction of flowering.
B) A brief dark period is not sufficient to trigger flowering.
C) Phytochrome is only active in the dark.
D) The circadian clock is less responsive during the day than at night.
E) The phytochrome response also requires cool nighttime temperatures.