Which word denotes a lively and enthusiastic attitude?

The word "ebullient" is characterized by a lively and enthusiastic attitude, making it the best choice for this question. It describes a state of being overflowing with energy and excitement, often expressing joy and exuberance. When someone is ebullient, they demonstrate a spirited and buoyant demeanor that can be infectious to those around them. This term typically reflects a high level of vivacity and eagerness, which aligns perfectly with the notion of having an enthusiastic attitude.

While the other words also convey strong feelings or characteristics, they each have slightly different connotations. "Zealous" often implies intense passion or fervor, particularly in pursuing a cause or objective. "Vibrant" generally refers to something full of life, energy, or color, which can describe a lively atmosphere or personality but doesn’t explicitly capture enthusiasm in the attitude sense. "Fervent," while indicating intense and passionate feelings, might not always encompass the lively, exuberant spirit that "ebullient" encapsulates. Thus, "ebullient" stands out as the most fitting term for describing a lively and enthusiastic attitude.