You will be given a definition of a task first, then some input of the task.
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: What is the difference between a food chain and a food web?  (A) A food chain always ends with a primary consumer. (B) A food web is made up of many food chains. (C) A food web only shows one flow of energy through the ecosystem. (D) A food chain is made up of many food webs?
Output:
B.