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).

[EX Q]: Question: Diatoms are microorganisms that produce sugars through the process of photosynthesis. Diatoms are an example of a microorganism that is __________.  (A) visible to the naked eye (B) disease-causing in humans (C) a primary producer (D) responsible for decompositio?
[EX A]: C.

[EX Q]: Question: Some objects are attracted by magnets. Which object is attracted by a magnet?  (A) an iron nail (B) an ice cube (C) a plastic knife (D) a wooden rule?
[EX A]: A.

[EX Q]: Question: A food chain shows how energy moves from one living thing to another. The chain always starts with ___.  (A) a plant or plant part (B) the smallest animal (C) the animal that was eaten last (D) the largest anima?
[EX A]:
A.