I need answers based on the table, educated guesses will do as well. Explain why having Cup 8 (the control) is important

[answerhappygod]

I need answers based on the table, educated guesses will do as
well.
Explain why having Cup 8 (the control) is important in the Part
1 activity.
If you were using the red cabbage acid-base indicator to test
stomach acid, what color would you expect the solution to turn and
why?
Imagine that you had one of your basic household substances
mixed with the cabbage solution, and then you used a straw to blow
carbon dioxide into it. What color would you expect it to turn?
Explain your answer.