Andrea is performing an experiment in which she needs to know when a strong acid is present. She is not sure which indicator to use, so she looks up the following table in her science textbook.

Indicator pH range
thymol Blue 1.2 - 2.8
phenol Red 6.4 - 8.0
phenolphthalein 8.0 - 10.0
trinitrobenzoic acid 12.0 - 13.4


According to the textbook, which indicator should Andrea use?

Hint: Neutral substances have a pH of 7. Acids have a pH that is less than 7, and bases have a pH that is greater than 7.
A.
phenolphthalein
B.
phenol Red
C.
thymol Blue
D.
trinitrobenzoic acid
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