The correct answer is C. X-rays.
A Coolidge tube is a type of vacuum tube that is used to produce X-rays. It was invented by William D. Coolidge in 1913. The tube consists of a cathode, an anode, and a filament. The cathode is heated, which causes electrons to be emitted. The electrons are then accelerated towards the anode by a high voltage. When the electrons hit the anode, they produce X-rays.
Radio waves are a type of electromagnetic radiation with wavelengths longer than those of visible light. They are used for a variety of purposes, including radio broadcasting, television broadcasting, and radar.
Microwaves are a type of electromagnetic radiation with wavelengths shorter than those of radio waves but longer than those of visible light. They are used for a variety of purposes, including microwave ovens, radar, and telecommunications.
Gamma rays are a type of electromagnetic radiation with the shortest wavelengths and highest frequencies. They are produced by radioactive decay and nuclear reactions.
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