Answer:
microwaves
Explanation:
Electromagnetic waves consist of waves of different wavelengths. Among the choices given, waves are ordered for increasing wavelengths as follows:
gamma rays --> ultraviolet waves --> infrared waves --> microwaves
So, microwaves are the waves with the longer wavelength among the given choices. This is the reason why they are used by the cell phone companies: in fact, since they have longer wavelengths, microwaves can travel longer distances without being absorbed by objects or obstacles, and so they are more reliable for broadcasting and telecommunications.
