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: Janette conducts an investigation to see which foods make her feel more fatigued. She eats one of four different foods each day at the same time for four days and then records how she feels. She asks her friend Carmen to do the same investigation to see if she gets similar results. Which would make the investigation most difficult to replicate?  
 (A) measuring the amount of fatigue (B) making sure the same foods are eaten (C) recording observations in the same chart (D) making sure the foods are at the same temperature
Example Output: A

Example Input: In a tug-of-war game, balanced forces are best represented when both teams cause the flag to  
 (A) stay in the middle. (B) fall to the ground. (C) move slowly in one direction. (D) be pulled quickly in one direction.
Example Output: A

Example Input: Technological advancements in the logging industry have had both negative and positive effects on forest ecosystems. The most likely negative effect of more efficient logging techniques is  
 (A) an increase in the time needed for transporting wood. (B) safer work environments for loggers. (C) a change in the chemical and physical makeup of land and water. (D) a decrease in the cost of wood and paper products.
Example Output:
C