\(v=f \lambda\)

\(=\lambda \text { is constant for an organ pipe }\)

\(v=\sqrt{\frac{\gamma R T}{M}}\)

\(v=\frac{1}{\sqrt{M}}\)

\(v\) is maximum when \(M\) is least. Thus, velocity of sound in air is maximum when \(M\) is least.

Since \(f \propto v\) so \(f \propto \frac{1}{\sqrt{M}}\)

Hence, frequency is maximum when \(M\) is least.

Hence, among options answer is \(H _2\).