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.

Ex Input:
Some types of bacteria can only live where oxygen is not present. These bacteria were well adapted to life on Earth over 2 billion years ago. Which of the following changes caused many of these bacteria to become extinct?
(A) the slow movement of tectonic plates (B) the varying temperatures of each season (C) an increase in volcanic activity under the oceans (D) an increase in the number of photosynthetic organisms

Ex Output:
D

Ex Input:
As water cools to a temperature of zero degrees Celsius and forms ice, water molecules tend to
(A) move farther apart. (B) vibrate rapidly. (C) flow more randomly. (D) gradually expand.

Ex Output:
A

Ex Input:
Scientists track an icy object with an orbit that ranges from the Kuiper Belt to a path between Earth and the Sun. How would this object best be classified?
(A) an asteroid (B) a comet (C) a meteor (D) a star

Ex Output:
B