Boil 0.5 g of the powdered tablets for 2 to 3 minutes with 10 mL of 5 M sodium hydroxide, cool and add an excess of 1　M sulfuric acid; a crystalline precipitate is produced. To a solution of the precipitate in water add iron (III) chloride solution R1; a（

Boil 0.5 g of the powdered tablets for 2 to 3 minutes with 10 mL of 5 M sodium hydroxide, cool and add an excess of 1　M sulfuric acid; a crystalline precipitate is produced. To a solution of the precipitate in water add iron (III) chloride solution R1; a（）colour is produced.
A.turquoise blue
B.deep violet
C.sandy brown
D.smoky grey
正确答案：deep violet