You will be given a definition of a task first, then some input of the task.
You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

On a class field trip, Zach took a walk through the woods using his senses. Zach made observations on the different sights, smells, and sounds in the woods. What system transferred the observations from his senses to his brain?
(A) nervous system (B) digestive system (C) circulatory system (D) respiratory system
Output:
A