Two tuning forks when sounded together produce 4 beats per second. One of the forks is in unison with 23 cm length of sonometer wire and other with 24 cm length of the same wire. The frequencies of the two tuning forks are

Beat frequency analysis
The production of 4 beats per second indicates that the frequencies differ by 4 Hz: $|f_1 - f_2| = 4$.

Length-frequency relationship
For a sonometer wire under constant tension, frequency is inversely proportional to length: $f \propto 1/L$. Given lengths 23 cm and 24 cm: $f_1 \cdot 23 = f_2 \cdot 24$. Since 23 cm < 24 cm, the corresponding frequency must be higher: $f_1 > f_2$.

Solving the system
From the beat frequency: $f_1 = f_2 + 4$. Substituting into the length relation: $23(f_2 + 4) = 24f_2$, which simplifies to $23f_2 + 92 = 24f_2$, yielding $f_2 = 92$ Hz. Then $f_1 = 92 + 4 = 96$ Hz.

The frequencies are 96 Hz and 92 Hz, corresponding to $\boxed{\text{A}}$.