What is defined as any event performed in a solemn and prescribed manner?

The correct choice is "rite." A rite is typically understood as a formal and ceremonial act that follows specific procedures and guidelines, often imbued with religious or cultural significance. Rites are performed in a solemn manner to mark important transitions or events, and they often contribute to the cultural and spiritual fabric of a community.

While both ritual and ceremony can also describe structured events, a rite is specifically characterized by its association with a significant purpose or meaning, often in a religious or spiritual context. This distinguishes it from a general ceremony, which may not necessarily have the same depth of significance. Tradition refers more to the broader practices and customs passed down through generations, rather than specifically to the acts performed.