When does phenolphthalein turn pink?

The correct answer is in the presence of a base.

Explanation:

Phenolphthalein is a pH indicator, which is generally colorless, however, it changes from pink to purple when encounters with the alkaline solutions. The compound phenolphthalein functions in a distinct way as it is colorless naturally, however, it turns from pink to dark pinkish color in alkaline solutions. Throughout the range of acidic pH levels, the compound stays colorless, however, it starts to turn pink at the pH of 8.2, that is, basic, and goes towards the bright purple color in stronger alkalines.

1.solid

2.carbon dioxide

3.helium