Answer
C. Any substance with a pH above 7.
Step-by-step explanation
Alkalis are water-soluble bases. bases that may be dissolved in water to produce OH⁻ ions are termed alkali. Alkali turns red litmus blue and is sour to taste. pH of an alkali substance is greater than 7.
Examples of alkali are NaOH, KOH, and Ca(OH)₂.
Hence, the answer which best describes an alkali is option C. Any substance with a pH above 7.