Final answer:
The best lunch choice for a child with glomerulonephritis, who has decreased urine output and high blood pressure, is grilled chicken with steamed vegetables, as it is low in sodium and has a moderate amount of protein, helping to manage the condition's symptoms.
Step-by-step explanation:
A child with glomerulonephritis has dietary restrictions due to decreased kidney function, which includes regulating protein, sodium, and fluid intake to reduce the excretory load on the kidneys. Considering the choices provided and the need for a low-sodium diet that is not heavy on protein, the best lunch option for this child would be A. Grilled chicken with steamed vegetables. This is because it is likely to contain less sodium than the other options and provides a balanced meal without excessive protein or added salts that could exacerbate blood pressure issues or edema.