Task: Question Answering
Input (English): A student has decided to investigate whether the number of flowers on a plant will increase if the water supply to the plant is increased. She has five pots of geranium plants to use in her experiment. What factor in the experiment should be varied for the five plants in order to answer the student's question?  
 (A) age of seedlings (B) temperature of water (C) volume of water (D) number of hours in sunlight
Output (English): C