Plants Could Readily Develop Seasonal Responses for Flowering Based on Temperature

Plants could readily develop seasonal responses for flowering based on temperature changes but have "elected" through evolution to manage their rhythms based on a comparison of daylight and darkness.Why has the day-night ratio system been selected?

A) Temperature has no effect upon plant biochemistry.
B) Temperature is a gradation but day/night is all-or-nothing.
C) A plant's nervous system is tuned to light stimuli and not to temperature stimuli.
D) Temperatures fluctuate widely across seasons and from year to year,but photoperiod comparisons are a more reliable indicator of season.