Identify the variables and controls in Carla's experiment.
Type of plant: Answer 1 Question 1
Identical incubators: Answer 2 Question 1
Plant receiving no carbon dioxide: Answer 3 Question 1
Height of plants after 30 days: Answer 4 Question 1
Lighting of incubators: Answer 5 Question 1
Addition of carbon dioxide: Answer 6 Question 1
Humidity in the incubators: Answer 7 Question 1