Select all the correct answers.

Regina is testing this hypothesis:
Higher relative humidity leads to faster growth in orchids.

She has designed an experiment in which she will grow orchids in terrariums of varying humidity levels. She will then observe how the humidity affects the growth of the plants.

Which of the following variables are the confounding variables that Regina should control for before beginning her experiment?

1.the amount of sunlight the plants receive

2.the temperature at which the plants grow

3.the type of soil in which the plants grow

4.the growth rate of each of the plants

5.the relative humidity inside each terrarium