Which of the following will turn Phenolphthalein pink?

Options

A. NaOH(aq)
B. HCl(aq)
C. `CH_3COOH` (aq)
D. `H_2O`

Explanation

To determine which of the following substances will turn phenolphthalein pink, we need to understand how phenolphthalein behaves in different pH environments.

### Step-by-Step Solution:

1. **Understanding Phenolphthalein**:
- Phenolphthalein is a pH indicator that changes color based on the acidity or basicity of a solution.
- It is colorless in acidic solutions (pH < 7) and turns pink in basic solutions (pH > 7).

2. **Identifying the Nature of Substances**:
- We need to analyze the substances provided in the options (not listed in the question but typically include acids and bases).
- Common examples include:
- Sodium Hydroxide (NaOH) - a strong base
- Hydrochloric Acid (HCl) - a strong acid
- Calcium Hydroxide (Ca(OH)₂) - a strong base
- Water (H₂O) - neutral

3. **Analyzing Each Substance**:
- **Sodium Hydroxide (NaOH)**: This is a strong base. When phenolphthalein is added, it will turn pink.
- **Hydrochloric Acid (HCl)**: This is a strong acid. When phenolphthalein is added, the solution remains colorless.
- **Calcium Hydroxide (Ca(OH)₂)**: This is also a strong base. When phenolphthalein is added, it will turn pink.
- **Water (H₂O)**: Water is neutral. When phenolphthalein is added, it remains colorless.

4. **Conclusion**:
- The substances that will turn phenolphthalein pink are the strong bases: Sodium Hydroxide (NaOH) and Calcium Hydroxide (Ca(OH)₂).
- Therefore, if the question provides options, the correct answers would be the bases.