Given a scientific passage and an answer, generate a question for the given answer.

[EX Q]: Passage: The heart is a muscular organ in the chest that consists mainly of cardiac muscle. It pumps blood through blood vessels by repeated, rhythmic contractions. Blood flows through four chambers of the heart when it beats. Heartbeat is controlled by electrical signals from special cells within the heart called the pacemaker. Answer: cardiac muscle
[EX A]: What type of muscle makes up most of the heart?

[EX Q]: Passage: As erosion by groundwater continues, the ceiling of a cave may collapse. The rock and soil above it sink into the ground. This forms a sinkhole on the surface. You can see an example of a sinkhole in Figure below . Some sinkholes are big enough to swallow vehicles and buildings. Answer: sinkhole
[EX A]: What is formed when the ceiling of an underground cave collapses?

[EX Q]: Passage: The physical behavior of gases is explained by the kinetic theory of gases. Answer: kinetic theory of gases
[EX A]:
What theory explains the physical behavior of gases?