Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: Volume is another way of measuring material. Gases cannot be easily weighed, but their volume can be determined quickly and accurately. Liquid chemicals as well as foods and beverages are also sold by volume. Gasoline for our cars and trucks is sold by the gallon. At the grocery store, we can buy a gallon of milk or a two-liter bottle of soda pop. Answer: material
Output:
Volume is another way of measuring what?