The argument, 'Sound is eternal, because it is produced', is fallacious because:

The correct option is: Middle term itself disproves the original proposition and proves its contradictory..

To understand why this argument is fallacious, let us break down the structure of the syllogism according to classical Indian logic (Nyaya):
1. Minor Term (Paksha): "Sound" (the subject about which the assertion is made).
2. Major Term (Sadhya): "Eternal" (the property that we are trying to prove about the subject).
3. Middle Term (Hetu): "Produced" (the reason or ground given to prove the assertion).

For an argument to be valid, the middle term must be logically compatible with the major term. However, in this case, the property of being "produced" (krtakatva) is incompatible with being "eternal" (nitya). In fact, whatever is produced or created must have a beginning and an end, which means it is necessarily non-eternal (anitya).

Thus, instead of proving that sound is eternal, the middle term ("produced") actually establishes the contradictory proposition: that sound is non-eternal. In Nyaya philosophy, this fallacy is called Viruddha (the contradictory middle), where the hetu directly refutes the sadhya it is intended to prove.