Question

stella wants to test the hypothesis \if carbon dioxide levels increase, the growth rate of sunflowers will increase.\ she places five young sunflower plants into similar containers and sets up pumps that release different amounts of carbon dioxide into each container. she plans to measure the daily height of the plants for two weeks and graph the data. which option would allow stella to set up a control group for the experiment? she should provide mist to each of the plants except one plant to keep the air moist and fertilize the plants she should give the plants receiving the least co₂ a little more oxygen to compensate for the difference in gases she should give all the flowers the same amount of water she should place one flower in a similar container, but not pump carbon dioxide into it.

Explanation:

In an experiment, a control group is a group that does not receive the treatment (in this case, the treatment is carbon dioxide). It is used for comparison.

• Option 1: Mist is not related to the variable (carbon dioxide) being tested.
• Option 2: Giving extra oxygen is introducing another variable and not related to setting up a proper control for carbon dioxide.
• Option 3: Giving same water is a constant (not a control for carbon dioxide).
• Option 4: Placing a flower in a similar container with no carbon - dioxide pumped in is a control group as it lacks the variable (carbon dioxide) that is being tested in the other groups.

Answer:

She should place one flower in a similar container, but not pump carbon dioxide into it.