Explanation:

Microwaves are electromagnetic wages with wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz (0.3 GHz) and 300 GHz. A microwave oven passes (nonionizing microwage radiation (at a frequency near 2.45 GHz) through food, causing dielectric heating by absorption of energy in the water, fats and sugar contained in the food. Bluetooth and Wi-Fi have many applications: setting up networks, printing, or transferring files. They also work in the given frequency range. All cordless sold in the US use the 1.9 GHz or 2.4-GHz bands.

Hence option 4th is correct.