There doesn't seem to be a clear answer, it is placed in the center when it's substances is on the corners it doesn't give anything else
Sorry this will probably be pretty long.
So think of the "control" as being something you yourself add to increase or decrease the effects in an experiment.
I'll give you an example so it is not as confusing.
Say you have decided to make an experiment on plants. Which plant can grow the fastest on which type of liquid? What is being added to this experiment? The liquid! Or all of the liquids you used. Like if you used Coke, Lime Gatorade, Orange Gatorade, and Water. Each drink will EFFECT each plant differently.
Hope I was of any hope?
The Answer is D cause of the people going back and forth.
Answer:
it's a physical change
Explanation:
there there was no burning it was grabbing and just cutting
