You are given a science question (hard-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 Q]: A student gives a red toy car a push on a wooden floor. The student then pushes the same red toy car on a cement floor. Which question is the student most likely investigating?
(A) How fast does a toy car usually roll? (B) What is the best way to make a toy car roll? (C) Which surface allows a toy car to roll farther? (D) Does color have an effect on the distance a toy car rolls?
[EX A]: C

[EX Q]: A main function of a plant's seed is to
(A) store food to be used during early development (B) attract pollen to be used during development (C) take in light energy to be used during photosynthesis (D) produce chlorophyll to be used during photosynthesis
[EX A]: A

[EX Q]: An experiment is performed with a sealed container. The container starts out with a temperature of 70 degrees F and an air pressure of 20 psi. The container is heated, and the pressure inside the container rises evenly with increased temperature. If the container is cooled back to 70 degrees F, what will the air pressure be?
(A) 10 psi (B) 20 psi (C) 30 psi (D) 40 psi
[EX A]:
B