Porphobilinogen in urine produces pink colour with-: (A) Fouchet's reagent, (B) Benedict's reagent, (C) Sodium nitroprusside, (D) Ehrlich's aldehyde reagent
Answer is D. Ehrlich's aldehyde reagent test is used for porphobilinogen and urobilinogen in urine. It is mainly used in acute intermittent porphyria.

About other options

Sodium nitroprusside (Rothera's test) → For ketone bodies
Benedict's test                                     → Glucose and other reducing sugars in urine
Fouchet's (barium sulphate) test         → Bile pigment (bilirubin)