In this task, you are given a multiple-choice question and you have to pick the correct option. Answer with option indexes (i.e., "A", "B", "C", and "D").

Example Input: A plane travels through what? (A) gas layers (B) plains (C) oceans (D) time
Example Output: A

Example Input: Cows know there is salt in a mineral lick because (A) they have receptors on their tongue that allow them to experience spice and seasonings (B) a cow in the ocean told them it was there (C) it's on their side of the pasture's fence (D) they evolved where there were great redwood trees
Example Output: A

Example Input: You find iron in (A) pure water (B) helium (C) our planet's crust (D) a cloud
Example Output:
C