Shawn is planning a scientific experiment. he wants to learn whether time of day has an effect on how far the roses in his mother's garden are open. he plans to measure the diameter of each flower on three rosebushes every hour during a week in the spring. what is the test variable (independent variable) in shawn's experiment?

Athe time of day

Bthe number of flowers

Cthe diameter of the flowers

Dthe time of year