I also believe the answer is A.
Disruptive selection or diversifying selection describes the changes in population genetics where extreme values for a trait are favored over intermediate values.
So according to this definition, the conclusion can be derived as :
The most common circumference(s) to be after 10 generations of diversifying selection will be greater than 2 cm and less than 2 cm.
She should conduct an expirement that proves whether the water changes the white flower or not
The changes in the grape juice happened due to the alcoholic fermentation of the grape juice that occurs due to the presence of aerobic bacteria. The presence of yeast is the main reason behind the process of fermentation taking place. The froth is produced due to the presence of the formation of acid and carbon dioxide.