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").

[EX Q]: What is a source of oxygen through photosynthesis? (A) lakes (B) car engines (C) sunflowers (D) people
[EX A]: C

[EX Q]: A 40 foot wide hole is found in the dessert. It's shaped like a ball had hit it. What could have happened? (A) something from space entered the atmosphere (B) a lizard built the hole (C) the moon's gravity pulled sand out of the hole (D) a dust storm filled it in
[EX A]: A

[EX Q]: Rocks collide with each other when moved by (A) dead valley girls (B) radio waves (C) glaciers (D) feathers
[EX A]:
C