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.
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Question: When gasoline in a car engine is burned, only about 15 percent of the gasoline is converted into mechanical energy. This is because most of the energy in the gasoline is  
 (A) transformed into heat. (B) stored for use at a later time. (C) changed into chemical energy. (D) used to make the vehicle move.

Answer: A


Question: Which pair of organisms benefits each other the most?  
 (A) birds building a nest in a bush (B) worms eating the roots of a plant (C) squirrels burying seeds from a tree (D) deer scraping their antlers on a tree

Answer: C


Question: A student wants to determine the effect of garlic on the growth of a fungus species. Several samples of fungus cultures are grown in the same amount of agar and light. Each sample is given a different amount of garlic. What is the independent variable in this investigation?  
 (A) amount of agar (B) amount of light (C) amount of garlic (D) amount of growth

Answer:
C