Plants Could Readily Develop Seasonal Responses Based on Temperature Changes

Plants could readily develop seasonal responses based on temperature changes, but have evolved 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.
E) Having a day-night system makes plants more likely to be an evolutionary success since animals follow day-night cycles as well.