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").

the presence of which of these is required for the formation of cavernous chambers? (A) some carbonated soda (B) some carbon dioxide (C) some carbonic acid (D) carbon monoxide gas
C

What does gravity cause substances on a planet? (A) things to move sideways (B) things to be moved upwards (C) things to descend to the lowest surface possible (D) things to stay in the same place
C

Some creatures can bring in prey by providing a source of light, such as (A) Lophiiformes (B) giant squid (C) sharks (D) crawfish
A