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

Input: Consider Input: Passage: Loudness refers to how loud or soft a sound seems to a listener. The loudness of sound is determined, in turn, by the intensity, or amount of energy, in sound waves. The unit of intensity is the decibel (dB). Answer: decibel

Output: What is the term used to measure the intensity of sound waves?

Input: Consider Input: Passage: Great volcanic explosions and glowing red rivers of lava are fascinating. All igneous rock comes from magma or lava. Remember that magma is molten rock that is below Earth's surface. Lava is molten rock at Earth's surface. Answer: magma or lava

Output: Where does all igneous rock come from?

Input: Consider Input: Passage: The stratosphere is the layer above the troposphere. The layer rises to about 50 kilometers (31 miles) above the surface. Answer: stratosphere
Output: What is the layer above the troposphere?