Question

which of these acids occurs naturally in the body and performs important regulatory functions?
○ carbonic acid
○ acetic acid
○ magnesium hydroxide
○ sodium hydroxide

Explanation:

1. Analyze each option:

• Carbonic acid ($\ce{H2CO3}$) is naturally present in the body, particularly in the blood, where it plays a key role in the bicarbonate buffer system to regulate blood pH.
• Acetic acid is found in vinegar and is not a major naturally - occurring regulatory acid in the human body.
• Magnesium hydroxide ($\ce{Mg(OH)2}$) is a base, not an acid, and is used as an antacid externally (not a natural regulatory substance in the body's normal physiological processes).
• Sodium hydroxide ($\ce{NaOH}$) is a strong base and is highly caustic, not present in the body for regulatory functions.

Answer:

A. carbonic acid