A scientist sets up an experiment to see if plants grow faster under only ultraviolet light. Which setup has the correct use of an experimental control?

Question

A. All of the plants are outside

B. some plants are outside, some plants are inside under an ultraviolet lamp

C. All the plants are under an ultraviolet lamp

D. An equal number of plants are placed outside and inside under an ultraviolet lamp

Answer 1

An equal number of plants are placed outside and inside under an ultraviolet lamp