A decrease in which of the following substances could be an explanation for enuresis in children?

• A. Dopamine.
• B. Antidiuretic hormone (ADH). 
• C. Insulin.
• D. Estrogen.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the term 'enuresis' — it refers to involuntary urination, especially by children at night (commonly known as bedwetting).
2. Step 2: Recognize the role of Antidiuretic Hormone (ADH) — ADH helps the kidneys manage the amount of water in the body by reducing urine production during sleep.
3. Step 3: Analyze how a decrease in ADH affects the body — lower levels of ADH lead to increased urine production at night, which can cause enuresis in children.
4. Step 4: Compare other substances listed (Dopamine, Insulin, Estrogen) — these do not primarily regulate urine production or water balance related to enuresis.
5. Step 5: Conclude that a decrease in Antidiuretic Hormone (ADH) is the most plausible explanation for enuresis in children due to its direct effect on urine concentration and volume.