A change in the contolled veriable. Such as a color change, state of matter change, a reaction like oader, bubbling or tempature change.
Answer:
Question 1.. A. Question 2.. C Question 3.. D. Question 4.. D. Question 5.. C.
Question 6.. A. Question 7.. B. Question 8.. B. Question 9.. B. Question 10.. B.
Explanation:
Potassium would be the correct answer.