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.

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
C

Some of the new cars being made can run on a renewable fuel that is made mostly from corn. Scientists are developing even more renewable fuels to replace gasoline. Why are renewable fuels most likely becoming more important?
(A) Renewable fuels release less energy. (B) Car fuel tanks are being made smaller. (C) The demand for gasoline is decreasing. (D) Nonrenewable fuel supplies are limited.
D

Several tomato plants are grown indoors next to a sunny window. The plants receive water and fertilizer and remain on the windowsill. What will most likely happen?
(A) Most of the leaves on the window side will wilt and die. (B) The roots of the plants will grow upward from the soil. (C) Water droplets will collect on the leaves facing away from the window. (D) The stem will bend toward the window.
D