a. a group

b. a period

c. an individual element

d. none of the above

I think it’s c because there all individual elements, not in a group

Aform of energy that is reflected or emitted from objects in the form of electrical and magnetic waves that can travel through space. there are many forms of  electromagnetic  energy including gamma rays, x rays, ultraviolet radiation, visible light, infrared radiation, microwaves and radio waves.