Suppose a student had a colorless unknown solution in a test tube. After adding 2 drops of phenolphthalein, the solution remained colorless. Select the possible identities of the unknown solution.
- 0.01 M HBr
- 0.01 M H₂SO₄
- H₂O
- 0.01 M NaCl
- 0.01 M LiOH