Explanation:

Correct: 1, 2, & 4

Brakes of motor vehicles: Friction from brakes can release magnetite particles.

Engines of motor vehicles: Combustion in engines can generate airborne magnetite particles.

Microwave stoves within homes do not generate magnetite particles as they do not involve combustion or friction..

Power plants: Combustion, especially coal burning, releases magnetite particles obviously through combustion process. .

Telephone lines: While not a primary source of magnetite particles, there is some research suggesting that corrosion from certain infrastructure, including telephone lines, might release such particles.