Which scenario describes a monopoly?

Company X and Company Y both produced farm tractors. Company X bought Company Y, making the merged company the largest supplier of tractors in the Midwest.
Berry Gordy Jr. founded Motown Records in 1959. Over time, the Black-owned business became one of the most success independent record labels.
In the late 1800s, Carnegie Steel controlled the steel supply in the United States. This allowed the company to set prices for steel throughout the United States.
A large supermarket chain moved into a neighborhood and offered low prices. Unable to compete, the neighborhood’s small independent grocery store closed.