Which of the following ions is a major cation electrolyte in the human body?

• A. Cl^-
• B. HCO_3^-
• C. SO_4^{2-}
• D. Na^+

Answer: (D)

Verified step by step guidance

1. Understand that electrolytes are ions that conduct electricity in the body and are essential for various physiological functions.
2. Recognize that cations are positively charged ions, while anions are negatively charged ions.
3. Identify the charge on each ion given: Cl^- (chloride) is an anion, HCO_3^- (bicarbonate) is an anion, SO_4^{2-} (sulfate) is an anion, and Na^+ (sodium) is a cation.
4. Recall that major cation electrolytes in the human body include Na^+, K^+, Ca^{2+}, and Mg^{2+}, with Na^+ being the most abundant extracellular cation.
5. Conclude that among the options, Na^+ is the major cation electrolyte, while the others are anions.