Answer: b. x-rays
Step-by-step explanation:
Option a is incorrect because infrared radiation is used to detect heat signatures, such as firefighters use to see if anyone is still inside a burning building.
Option b is correct because x-rays are used to take pictures of bones and internal structures to see what may be causing pain.
Option c is incorrect because visible light is what we can see without any technology.
Option d is incorrect because that's what carries sound.