An organic compound 'A' with molecular formula CH₄O reacts with HI to give an alkyl iodide which than reacts with potassium cyanide to produce 'B'. Compound 'B' on reduction followed by reaction with HNO₂ gives an alcohol which on oxidation gives 'C'. Compound 'C' on oxidation followed by reaction with CH₃MgBr gives 'D' which on hydrolysis gives compound 'E' which is also an alcohol. 

Which of the following is a method of preparation of HNO₂?

HCl or H₂SO₄  + NaNO₂

Here, the correct answer will be HCl or H₂SO₄  + NaNO₂ 

HNO₂ i.e., nitrous acid can be prepared by the action of dilute HCl or H₂SO₄ on NaNO₂ or any other nitrite.