What was a significant development in architecture during the Middle Ages?

The use of flying buttresses in cathedrals was a significant development in architecture during the Middle Ages because it allowed for the construction of larger and taller buildings while also enabling the inclusion of large stained glass windows. This architectural innovation was particularly prominent in Gothic architecture, which flourished in the later part of the Middle Ages, around the 12th to 16th centuries.

Flying buttresses are external supports that transfer the weight of the roof and walls outward, allowing for thinner walls and more open interior spaces. This design facilitated the creation of grand cathedrals, most notably exemplified by structures such as Notre-Dame de Paris and Chartres Cathedral. The incorporation of these buttresses not only improved the structural integrity of the buildings but also transformed their aesthetic appeal, leading to the iconic soaring heights and intricate designs characteristic of Gothic cathedrals.

In contrast, the other options do not represent significant medieval architectural advancements. The invention of skyscrapers and modern office buildings refers to developments that occurred much later, during the industrial era. Log cabins, while historically significant, pertain more to domestic architecture and do not reflect the monumental achievements epitomized by the ecclesiastical structures of the Middle Ages.