On adding 1 mL solution of 10% NaCl to 10 mL gold solution in the presence of 0.25 g of starch, the coagulation is just prevented. Starch has the gold number equal to:
(a) 0.25 (b) 2.5
(c) 250 (d) 0.025
(c) Gold no. is to be reported in mg.