I need hel!!
ASAP
Which of the following procedures would provide the best data to test the effect of daylight hours on the number of blooms on rose bushes?

A. Count the number of blooms on rose bushes in different areas of the world that have different amounts of daylight.

B. Research the kinds of rose bushes that have the highest number of blooms to see how much daylight they need.

C. Collect data on the number of blooms on rose bushes all grown under identical conditions, except hours of daylight.

D. Study a single rose bush during different seasons and under different amounts of daylight to see when it has the most blooms.