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]: 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
[A]: A


[Q]: A town in northern Arkansas experienced colder than normal temperatures during part of the winter. Which change was most likely responsible for this?  
 (A) A southward dip in the jet stream (B) A northward movement of the jet stream (C) The Coriolis effect creating a low pressure area (D) The Coriolis effect creating a high pressure area
[A]: A


[Q]: Some species of bacteria produce a substance that is toxic to insects but harmless to humans. Scientists have isolated the gene that controls production of this substance. Which of the following is the best reason for inserting this gene into corn plants?  
 (A) The corn will grow faster. (B) Less fertilizer will be needed. (C) Fewer pesticides will be needed. (D) The corn will be more nutritious.
[A]:
C