Which of the following statements about the thiosulphate ion are correct?

AWith dilute HCl it gives $SO X_{2}$ and a turbidity of sulphur.
BIt reduces iodine to iodide, being oxidised to tetrathionate.
CWith excess $AgNO X_{3}$ it gives a white precipitate that turns black on standing.
DWith alkaline sodium nitroprusside it gives the purple $Na X_{4} [Fe (CN) X_{5} NOS]$ , like $S X^{2 -}$ .

Answer: A, B, C

Statement 1 follows from

S X_{2} O X_{3} X^{2 -} + 2 H X^{+} S + SO X_{2} + H X_{2} O

. Statement 2:

2 S X_{2} O X_{3} X^{2 -} + I X_{2} S X_{4} O X_{6} X^{2 -} + 2 I X^{-}

. Statement 3:

Ag X_{2} S X_{2} O X_{3}

hydrolyses to black

Ag X_{2} S

. Statement 4 describes the test for sulphide, not thiosulphate.