The coagulation of 200 mL of a positive colloid took place when 0.73 g HCl was added to it without changing the volume much. The flocculation value of HCl for the colloid is:

200 mL of the sol required = 0.73 g HCl.
The molecular weight of HCl is 36.5 g/mol.
Number of moles of HCl = (0.73 g) / (36.5 g/mol) = 0.02 mol
Concentration of HCl = (0.02 mol) / (0.2 L) = 0.1 mol/L = 0.1 M
Flocculation value is defined as the minimum concentration of an electrolyte required to cause coagulation of a colloid. In this case, 0.1 M HCl caused coagulation. Therefore, the flocculation value of HCl for the colloid is 0.1 M or 0.1 millimoles/litre which translates to 0.1 x 36.5 = 3.65 mg/L. Since the options are given in g/L the equivalent of 3.65 mg/L in g/L is 3.65/1000 = 0.00365 g/L. Considering the given options, the closest value is 0.365 g/L.