Answer: D
1:2 means three ions, so the complex ion is [Co(NHX3)X5Cl]X2+ with two free ClX−: [Co(NHX3)X5Cl]ClX2. Only free chloride precipitates, giving 2 mol AgCl. Co(III) is 3d6 and low spin, so t2g6 with 0 unpaired electrons and d2sp3 hybridisation.