28. What variable had the same value for all the water samples in Study 1 but did not have the same value for all the water samples in Study 2 ?
Your Answer is
Correct Answer is J
Explanation
The first sentence of the text part of Study 1 says that the pH of the three solutions is the same; and by looking at figure 2, it can be found that one of the independent variables of Study 2 is pH, so choose J