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.

A hearing aid is a small device that contains an amplifier, a battery, a microphone, and a speaker. Which part of a hearing aid functions to detect sounds in the user's environment?
(A) the amplifier (B) the battery (C) the microphone (D) the speaker
C

On a field trip, a student holds a frog and reports that it has slippery skin. This is an example of
(A) a measurement (B) a prediction (C) an explanation (D) an observation
D

Students are comparing different rocks. What do all rocks have in common?
(A) Rocks are made of one or more minerals. (B) Rocks are made of two or more elements. (C) Rocks are made of magma and sediments. (D) Rocks are made of sand changed by pressure.
A