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.

[Q]: Dumping toxic chemicals into a pond would most likely result in
(A) an increase in oxygen levels in the pond. (B) plants near the pond growing more quickly. (C) the toxic chemicals having no effect on the pond. (D) fish in the pond being harmed or dying off.
[A]: D

[Q]: Scientists have discovered fossils of the same organisms in many different parts of the world. These fossils provide evidence that
(A) the continents were once joined together (B) most life-forms that existed in the past are still present today (C) most of Earth's surface was once covered by molten rock (D) rocks have been transformed from one type to another
[A]: A

[Q]: What is the result of cellular respiration?
(A) Energy for cell processes is released. (B) Oxygen is released for photosynthesis. (C) Cells undergo decomposition. (D) Nutrients are excreted to prevent the buildup of body fat.
[A]:
A