My question reads as follows:
"What's the most useful reagent for the gravimetric analysis of silver from the options below: A. Sodium nitrate B. Barium carbonate C. Potassium sulphate D. Ammonium chloride"
I can rule out A and C as they do not form a silver precipitate with a solution containing silver. However, both B and D can form a silver precipitate so I am not sure which of them would be the most useful.