The correct answer is
D. Orthostatic proteinuria is very common. It occurs when the total urinary protein excretion rate is higher while the child is in an upright position. It is asymptomatic, and there is no associated increase in renal disease. Diagnosis is made by obtaining a "first morning" urine before the child has had much time in an upright position.

Acute glomerulonephritis (choice A) usually presents with gross hematuria and may or may not be associated with edema. Severe glomerular injury would be associated with proteinuria.

IgA nephropathy (choice B) usually presents with episodic, asymptomatic gross hematuria, with microhematuria occurring between episodes. Proteinuria occurs in more severe, atypical cases.

Minimal change disease (choice C) is characterized by proteinuria, hyperlipidemia, edema, and hypoproteinemia. The proteinuria is usually greater than 2+.

A urinary tract infection (choice E) may present with 1+ proteinuria but the patient would also more typically have hematuria. The fact that there are no bacteria would make a urinary tract infection less likely.