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.

[Q]: Which force produces energy as heat?
(A) pull (B) gravity (C) friction (D) magnetic
[A]: C

[Q]: Ribosomes present in a particular cell are smaller than those found in plants. In which taxonomic group or groups could the cell be classified?
(A) fungi only (B) archaea only (C) bacteria or archaea (D) bacteria or fungi
[A]: C

[Q]: When riding a roller coaster, an electric motor pulls the roller coaster to the top of the first hill. What force pulls the roller coaster down the hill?
(A) friction (B) speed (C) gravity (D) mass
[A]:
C