A biology student wanted to determine if using fertilizer would promote plant growth. One hundred plants were randomly assigned to one of two groups: one that used the fertilizer, and one that did not use a fertilizer. Each plant was planted in the same amount of soil and given the same amount of water and light. Which of the following describes the benefit of using control in this experiment?

By controlling the amount of soil, water, and light in the experiment, we eliminate the need to have a control group.
By controlling the amount of soil, water, and light that may influence the response variable, we reduce variability in the response variable.
By controlling the amount of soil, water, and light that may influence the response variable, we eliminate variability in the response variable.
By controlling the amount of soil, water, and light, the differences observed in the response variable can be attributed to those variables that were controlled.