What are bases that are soluble in water called?

The correct option is Alkalis.

Bases are chemical substances that accept protons or release hydroxide ions in aqueous solutions. While many bases do not dissolve in water, bases that are soluble in water are specifically called alkalis.

Common examples of alkalis include sodium hydroxide (NaOH) and potassium hydroxide (KOH). When dissolved in water, alkalis produce hydroxide ions (OH^-), resulting in an alkaline solution with a pH value greater than 7.

Let us briefly review the other options:
- Alkanes: Saturated hydrocarbons with single covalent bonds between carbon atoms.
- Acids: Chemical compounds that yield hydrogen ions (H⁺) in water, having a pH less than 7.
- Alkenes: Unsaturated hydrocarbons containing at least one carbon-carbon double bond.