Answer:
I can't definitively answer this because I don't know the experiment, but I can help.
Step-by-step explanation:
The "control group" of an experiment is like a dry simulation, where there is no variables changed across all the different trials you do. This is different from a dependent variable or an independent variable. Using your newfound knowledge of what a control group is you can automatically cross off the last option.
Since I cannot see what your experiment was I can't give you which of the top 3 answers it is however. You need to look at which one has no change.
If I were to blindly guess I would say the top option seems like the most likely answer.