A class was performing an experiment to discover the pH values of some common household substances. The results of three groups are shown in the table below. Substance
Group 1 pH
Group 2 pH
Group 3 pH
Lemon juice
2.2
2.2
2.1
Vinegar
2.8
2.8
8.2
Baking soda
8.4
8.5
8.4
Milk of magnesia
10.2
10.3
10.2

Which statement best describes evidence that Group 3’s data are less valid than the data for the other two groups?
a. Group 3’s pH value for lemon juice is lower than the values of the other two groups.
b. Group 3’s pH value for vinegar is much higher than the values of the other two groups.
c. Group 3’s pH value for baking soda does not exactly match the values of the other two groups.
d. Group 3’s pH value for milk of magnesia is different from the value obtained by Group 2.