Given the task definition and input, reply with output. In this subtask, you will answer a simple science question. Please indicate the correct answer. If you're not sure about the answer, choose the last option "I don't know". Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D', 'E'. The "A"-"D" responses correspond to the answer options mentioned in the input. There is a 5th option "E" which should be used for questions for which you're not sure about the answer (e.g., when the questions do not provide enough information to answer).

Question: Ella is raising fish in an aquarium. Which is the best estimate for the amount of water needed to fill a household aquarium that holds three fish?  (A) 25 milliliters (B) 25 centiliters (C) 25 liters (D) 25 kiloliter?

C.