To solve this problem, we need to determine which factor causes an increase in sodium reabsorption in the distal convoluted tubule. Let's analyze each option:$\newline \bullet$Option 1: Increase in aldosterone levels$\newline$ - Aldosterone is a hormone produced by the adrenal cortex.$\newline$ - It increases sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron.$\newline$ - This is achieved by increasing the expression of sodium channels and sodium-potassium pumps.$\newline$ - Therefore, an increase in aldosterone levels leads to increased sodium reabsorption.$\newline \bullet$Option 2: Decrease in antidiuretic hormone levels$\newline$ - Antidiuretic hormone (ADH) primarily affects water reabsorption, not sodium reabsorption.$\newline$ - A decrease in ADH levels would lead to decreased water reabsorption, not directly affecting sodium reabsorption.$\newline \bullet$Option 3: Decrease in aldosterone levels$\newline$ - A decrease in aldosterone levels would lead to decreased sodium reabsorption, as aldosterone promotes sodium reabsorption.$\newline \bullet$Option 4: Decrease in antidiuretic hormone levels$\newline$ - As mentioned earlier, ADH primarily affects water reabsorption, not sodium reabsorption.$\newline$ - A decrease in ADH levels does not directly increase sodium reabsorption.$\newline$Based on the analysis, the correct option is:$\newline$Option 1: Increase in aldosterone levels.