To determine the effect of color of light on plant growth, 4 groups of bean plants were grown under the light conditions below.

group 1—under red light group 2—under green light

group 3—under violet light group 4—in normal, white light
which of the variables below should be held constant?

question 3 options:

a. how much each plant grows

b. the amount of light each group of plants receives

c. the color of light each group of plants receives

d. all of the above

The correct answer will be option-B

Explanation:

In an experiment, the variable which is kept constant throughout the experiment is known as the constant variable. The constant variable does not change and controls the fate of the experiment as changing the constant variable can cause an error in the results.

In the given question, the study was performed to test the effect of color on plant growth by using different colors of light in which the amount of light must be kept constant as the growth of the plant is influenced by the amount of light also.

Thus, Option-B is the correct answer.