Which type of poem is characterized by being written as letters?

The correct answer is the type of poem known as an epistolary poem. This form is specifically characterized by its structure, which mimics the style of letters or correspondence. In an epistolary poem, the poet typically writes as if they are addressing another individual directly, creating an intimate and personal connection. This format allows the poet to express thoughts, emotions, and reflections much like one would in a private letter, making it unique among poetic forms.

In contrast, the other types of poems listed do not share this letter-like quality. An ode is a lyrical poem that praises or reflects on a subject, often in a formal style. A limerick is a humorous five-line poem with a specific rhythm and rhyme scheme, typically light-hearted and playful. A haiku is a traditional Japanese form that consists of three lines with a specific syllable structure (5-7-5) and usually focuses on nature or a moment in time. Each of these forms has its own distinct characteristics that set them apart from an epistolary poem.