A) Incorrect. Nephrotic syndrome is a different kidney disorder characterized by heavy proteinuria and edema but is not characterized by crescent-shaped structures in the glomeruli.

B) Correct. Rapidly progressive glomerulonephritis (RPGN) is characterized by the formation of crescent-shaped structures within the glomeruli and is a complication of glomerulonephritis.

C) Incorrect. Polycystic kidney disease involves the development of cysts within the kidneys and is unrelated to crescent formation in glomerulonephritis.

D) Incorrect. Acute pyelonephritis is a different kidney condition caused by a bacterial infection of the renal pelvis and is not characterized by crescent-shaped structures in the glomeruli.