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.

Example input: Which event can cause a large rock to become soil over time? 
 (A) decaying (B) an earthquake (C) a landslide (D) weathering
Example output: D
Example explanation: Under the action of heat, cold, rain, wind, and other atmospheric factors, the rock breaks down physically into small fragments that become the parent material of the soil. Also, atmospheric factors change according to weather.
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