What best describes a characteristic of a jet stream?

A jet stream is a fast-flowing, narrow band of air located in the upper levels of the atmosphere, typically between 6 to 12 miles above sea level. It flows from west to east and can reach speeds of over 200 miles per hour. Jet streams play a crucial role in shaping weather patterns, influencing storm systems, and affecting temperature variations across regions. They are often found at the boundaries between different air masses, such as polar and tropical air.