Sodium thiosulphate solution turn cloudy when it reacts with nitric acid:
a. due to the formation nano3
b. due to the evolution of so2 gas
c. due to the formation of s.
d. none of the above.

The solution turn cloudy due to the formation of elemental sulphur as precipitate.

Explanation:

Nitric acid is a very good oxidizing agent and it oxidizes sodium thiosulphate

into sodium sulphate.

The following reaction takes place when nitric acid reacts with sodium thiosulphate.

Na₂S₂O₃+2HNO₃→Na₂SO₄+S+2NO₂+H₂O

On reaction of sodium thiosulphate  with nitric acid the following products are obtained:

1.Sodium sulphate(Na₂SO₄)

2.Precipitate of elemental sulphur(S)

3. Nitrogen dioxide (NO₂)

4.water molecule(H₂O)

The overall solution turns cloudy because of the formation of elemental sulphur as precipitate.