Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

[Q]: Question: Sensory organs that respond to particular sensory stimuli contain cells called what? Answer: sensory receptors
[A]: Sensory organs such as the eyes contain cells called sensory receptors that respond to particular sensory stimuli.

[Q]: Question: What is the process of changing something from a gas to a liquid? Answer: condensation
[A]: Condensation is the change of state from a gas to a liquid.

[Q]: Question: What is the minimum number of pulleys needed for a compound pulley? Answer: 2
[A]:
Single pulleys may be fixed or moveable. Compound pulleys consist of two or more pulleys.