What do you call a base that dissolves in water?

Alkali

The correct answer is option 1. Alkali.

A base that dissolves in water is called an alkali.

Alkali metals are a group of highly reactive metals in the first column of the periodic table. They readily form soluble bases when they react with water.

Alkenes, aldehydes, and alcohols are all organic functional groups, not related to the solubility of bases in water.