An electrically maintained tuning fork oscillates with a constant...

The frequency of the sound produced is determined by the source, which is the electrically maintained tuning fork. Since it oscillates with a constant frequency, the frequency $f$ and time period $T$ of the produced sound remain constant.

The velocity of sound in a gas is given by $v = \sqrt{\dfrac{\gamma RT}{M}}$.

As the temperature $T$ of the surrounding air increases, the velocity of sound $v$ increases.

The wavelength of the sound wave is given by $\lambda = \dfrac{v}{f}$.

Since $v$ increases and $f$ is constant, the wavelength $\lambda$ also increases.

Therefore, the sound will exhibit a larger wavelength and a larger velocity.