Which will act as a buffer solution

Options

A. `200 mol N//10 NaOH+ 100ml N//20 HCl`
B. `100ml 0.1 N NaOH + 100 ml 0.1 N HCl`
C. `100 mol 0.1 N NaOH+50 ml 0.2 N CH_(3)COOH`
D. `100 ml 0.1 N NaOH + 150 ml 0.1 N HCN`

Answer

4

Explanation

For Buffer solution, we should have
two constituents `i.e. a ` weak & it's conjugate base
Hence `(4)` Ans.