What are the avenues of water loss from the body?

• A. Only urine.
• B. Water loss occurs only via respiration.
• C. Water vapor through respiration, sweating, urine, and feces.
• D. Water loss occurs through sweating alone.

Answer: (C)

Water balance depends on multiple routes of loss, not just one. The body continuously loses water through insensible routes (water vapor in air we exhale and evaporation from the skin) and through sensible routes (sweating) as well as through the digestive and urinary systems. The best answer acknowledges all of these pathways: water vapor in exhaled air, evaporation from the skin via sweating, urine, and feces. Each pathway contributes to daily water loss, so total loss comes from a combination of these routes rather than a single one.

Choosing only urine would miss insensible losses; respiration-only would miss urine, feces, and sweating; sweating-alone would miss urine and fecal water loss.