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).
Example: Question: When a guitar string is plucked, sound is produced by  (A) the size of the guitar. (B) the metal on the guitar. (C) the wood on the guitar. (D) the vibrations of the string.
Example solution: D.
Example explanation: We know that the vibrations of the string produces sound in a guitar. So, the correct answer has to be "D".

Problem: Question: All natural resources on Earth are either renewable or nonrenewable. Whether a resource is renewable or nonrenewable depends on how fast or slow the resource is replaced. If the resource is used faster than it is replaced, then the resource will, in time, disappear. Which activity shows the use of a nonrenewable natural resource?  (A) A group of people swims in a river. (B) A construction crew builds an iron bridge. (C) A farmer grows vegetables to sell at a local market. (D) A person bakes a cake with electricity produced by a hydroelectric power plant?

Solution: B.