Antonio’s teacher challenged the class to create an experiment that tests how air temperature affects plant growth. Antonio’s group created their experiment using two green bean plants and one lima bean plant. During the experiment, the green beans were placed in direct sunlight. The lima beans were placed in direct sunlight with an aluminum cover. The table shows the proposed experimental design. The teacher handed back their assignment and asked the group to correct an error in their experimental design. What correction needs to be made?

Their experimental procedure was too advanced.

They should have only one tested variable.

They should have included another type of bean.

There was no outcome variable.