Which of these is not a natural source of radiation? A) Food and drink
B) medical x-rays
C) Cosmic rays

Food and drink

Explanation:

theoretically, you can heat object to a point in which they'll radiate rays, but not food and drinks

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.

grav potential energy