The correct answer is (b) BAG-4
The explanation: BAG-4 filler metal is used for carbide tip brazing and is composed of 39-41% Ag, 29-31% Cu, 26-30% Zn, 1.5-2.5% Ni, and 0.15% of other elements. BAG-1 freely flows into low and narrow capillary joints. BAG-8 filler metal is used in a controlled atmosphere or vacuum brazing, whereas BAG-18 is used for brazing of ferrous and non-ferrous alloys without flux.