Question

what is one thing x - rays are used for?
to look inside of luggage at airport security scanners
to receive tv signals
to cook food

Explanation:

X - rays have the property of being able to penetrate certain materials. Airport security scanners use this property to look inside luggage. TV signals are typically received using radio - frequency waves (not X - rays). Cooking food is usually done using methods like heat transfer (e.g., conduction, convection, microwave radiation for microwaves, but not X - rays).

Answer:

To look inside of luggage at airport security scanners.