The correct answer is A. Ceramic balls can be used to replace steel in ball bearings.
Ceramic balls are made of a hard, brittle material such as silicon nitride or zirconia. They are often used in applications where steel balls would wear out too quickly, such as in high-speed machinery or in applications where there is a lot of friction. Ceramic balls are also non-magnetic, which makes them useful in applications where magnetic fields would interfere with the operation of the equipment.
B. Rifle fire is not a good application for ceramic balls. Ceramic balls are brittle and can shatter if they are hit by a bullet. This could cause serious injury or death.
C. Ceramic balls can be used on a hard surface, but they are not as durable as steel balls and may wear out more quickly.
D. None of the above is not the correct answer. Ceramic balls can be used to replace steel in ball bearings, but they are not suitable for rifle fire or use on a hard surface.