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

Input: Consider Input: Passage: Renewable resources are natural resources that can be replaced in a relatively short period of time or are virtually limitless in supply. Renewable energy resources include sunlight, moving water, wind, biomass, and geothermal energy. Each of these energy resources is described in Table below . Resources such as sunlight and wind are limitless in supply, so they will never run out. Besides their availability, renewable energy resources also have the advantage of producing little if any pollution and not contributing to global warming. The technology needed to gather energy from renewable resources is currently expensive to install, but most of the resources themselves are free for the taking. Answer: renewable resources

Output: What are natural resources which can be replaced in a relatively short period called?

Input: Consider Input: Passage: Some people think that gravity moves food through the esophagus. If that were true, food would move through the esophagus only when you are sitting or standing upright. In fact, because of peristalsis, food can move through the esophagus no matter what position you are ineven upside down! Just don't try to swallow food when you are upside downyou could choke!. Answer: peristalsis

Output: What process moves food through the esophagus no matter which position the body is in?

Input: Consider Input: Passage: Thermal Expansion The intermolecular forces in liquids are strong enough to keep them from expanding significantly when heated (typically only a few percent over a 100C temperature range). Thus the volumes of liquids are somewhat fixed. Notice from Table 11.1 "The Density of Water at Various Temperatures" that the density of water, for example, changes by only about 3% over a 90-degree temperature range. Table 11.1 The Density of Water at Various Temperatures. Answer: intermolecular forces
Output: What forces in liquids are strong enough to keep them from expanding significantly when heated?