What materials are known to make up a good type of permanent magnet?

The correct choice identifies aluminum, nickel, and cobalt as components that contribute to the creation of good permanent magnets. These materials are significant due to their magnetic properties. Specifically, nickel and cobalt are ferromagnetic materials, which means they can be magnetized and maintain their magnetic properties over time.

Aluminum, while not a ferromagnetic material by itself, is often used alongside nickel and cobalt in various alloys, which can enhance the overall magnetic properties of the material. This combination leads to improved performance in applications where strong, stable magnetic fields are required, such as in electric motors, generators, and magnetic resonance imaging (MRI) machines.

The other choices include materials that either lack the appropriate magnetic properties or do not retain magnetization effectively. For instance, copper and silver are excellent conductors of electricity but do not exhibit ferromagnetism, while materials like lead, zinc, titanium, and brass also do not serve as effective permanent magnets in practical applications. Thus, the combination of aluminum, nickel, and cobalt stands out for creating durable and effective permanent magnets.