Final answer:
Above-ground storage tanks can be either pressurized or nonpressurized. Pressurized tanks hold substances under high pressure, while nonpressurized tanks store substances at atmospheric pressure.
Step-by-step explanation:
Above-ground storage tanks can be either pressurized or nonpressurized, depending on their design and purpose. Pressurized tanks are designed to hold substances under high pressure, while nonpressurized tanks store substances at atmospheric pressure. For example, a metal cylinder used to store gas at high pressure is a pressurized tank, while a tank used to store oil or water is often nonpressurized.
It's important to note that different types of substances require different storage conditions, and the choice between pressurized and nonpressurized tanks is determined by the specific needs and requirements of the substance being stored.