Radio waves are primarily used to
image people's bones
absorb harmful radiations
transmit cellular phone signals
detect the location of objects that emit heat

Radio waves are primarily used to transmit cellular phone signals.

Explanation:

A radio wave is a wave in the form of electromagnetic radiation with wavelengths ranging from roughly a thousand kilometers to a millimeter, so in the frequency range of a few hundred Hz to a few hundred GHz. Radio waves are used in communication technology to transfer information from a radio station to one or more receivers. Radio waves were discovered by Heinrich Rudolf Hertz in 1886.

The transmitter transmits via an antenna, whether or not directed, the radio waves that, after propagation through the space, are picked up by the antenna of the receiver. The radio wave serves as a carrier for the information to be transmitted, which is present as a variation in the amplitude (AM) or in the frequency (FM).