Answer:
1. D- All of the above
2. B- The material the acid is poured on
3. C- Mass of the ball
4. A- Temperature
Explanation:
2. The control variable is what stays the same so the material the acid is poured on must be the same as different materials have different reactions to acids.
3. The independent variable is what's being changed and in this experiment the mass of the ball is changed each time
4. The independent variable is what's being changed and in this experiment the temperature is different in each cup.
Hope this helped! :)