You will be given a definition of a task first, then an example. Follow the example to solve a new instance 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.

Which part of a bicycle BEST moves in a circle?
(A) Seat (B) Frame (C) Foot pedal (D) Kickstand
Solution: C
Why? Seat, frame and Kickstand are static parts of the bicycle, even when bicycle moves. Foot pedal moves in a circle as bicycle moves.

New input: During a lab investigation, students were asked to determine the best way to clean up an oil spill using different materials. Investigation Materials filter paper foam sponge metal wire screen thin sock filled with hair The students tested the materials by placing each material into separate buckets containing oil and water. They recorded their observations on which material absorbed the most oil. Why would the students' teacher ask them to repeat their tests?
(A) to determine if water and oil can be separated (B) to learn more about how to protect wildlife during an oil spill (C) to improve the chances of obtaining accurate oil cleanup results (D) to increase the total amount of oil removed from each container
Solution:
C