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).

Let me give you an 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.
The answer to this example can be: D.
Here is why: We know that the vibrations of the string produces sound in a guitar. So, the correct answer has to be "D".

OK. solve this:
Question: Which is most like the way a stem supports a flower?  (A) the way water supports a boat crossing a river (B) the way a flagpole supports a flag in the schoolyard (C) the way bookends support books on a shelf (D) the way a belt supports pants on a person's wais?
Answer:
B.