Final answer:
After 1 week of treatment with prednisone, a school-age child with primary nephrotic syndrome would likely show an improved appetite and weight loss as signs of the medication's effectiveness.
Step-by-step explanation:
A school-age child with primary nephrotic syndrome who is taking prednisone and showing signs of efficacy would most likely manifest an improved appetite and weight loss (c) after 1 week of treatment. This is because prednisone is a corticosteroid that helps reduce inflammation and suppress the immune system, leading to decreased proteinuria (protein levels in the urine), reduced swelling, and an increased appetite due to its catabolic effects. An effective response to the medication would not typically include increased urine protein levels (a), persistent edema and weight gain (b), or decreased urine output and dark-colored urine (d), as these are signs of ongoing nephrotic syndrome or potential side effects of the medication, respectively.