In the questions given below, a sentence is given,

Solution

Part C is the odd part. B opens the sentence by introducing the subject — the structural ingenuity of flying buttresses and what it allowed.  E directly continues B by completing that thought — it tells us what builders were allowed to do: construct walls of unprecedented height and lightness.  A then naturally follows by stating the broader significance of what these builders achieved — the cathedral stood as a testament to.  D concludes the sentence by telling us what the cathedral was a testament to — human ambition, devotion, and the era in which (it was built). So the logical chain is: B → E → A → D, forming — "The structural ingenuity of flying buttresses allowed builders to construct walls of unprecedented height and lightness, and the medieval cathedral stood as a testament to human ambition, devotion, and the era in which it was built." C is the odd part because it introduces an entirely different idea — that Gothic architecture reached its most (presumably its peak) — which is a separate evaluative claim not connected to or developed by any other part. No other part discusses the peak or zenith of Gothic architecture as a style, making C an isolated fragment that breaks the logical chain entirely.