Task: Question Understanding
Input (English): Question: Students are performing an experiment to determine what effect adding fertilizer has on a plant's flower blossoms. Each day, they observe and measure the flowers on both the fertilized plant and the unfertilized control plant. All of the following might be useful observations except ___. (A) how many blooms each plant has (B) the number of petals on each plant's blooms (C) how large each plant's blooms are (D) how wide the leaves on each plant are?
Output (English): experiment, effect, adding, fertilizer, blossoms., observe, measure, flowers, useful, observations, except