In contrast to the intricate structures of Gothic cathedrals, the Parthenon was based on simpler, classical principles.

✓ Correct Answer: Option B

The original sentence makes an illogical comparison: 'structures' of cathedrals vs. 'the Parthenon' itself. A comparison must be between like items. Option B correctly compares 'structures' to 'the Parthenon's design,' ensuring a logical and parallel comparison.