Which metric term describes a line of verse with just one foot and is the simplest form?

The correct choice is the term that refers specifically to a line of verse containing only one foot, making it the most basic unit of meter in poetry. In this context, a foot is a combination of stressed and unstressed syllables. A line classified as having one foot is termed a monometer. This is the simplest form of line in terms of meter because it consists of only a single measured unit, creating a concise and straightforward rhythmic quality.

In contrast, terms like dimeter, trimeter, and hexameter refer to lines with more feet: dimeter has two feet, trimeter has three feet, and hexameter has six feet. Each of these introduces additional complexity and cadence to the verse compared to the simplicity of a monometer. Therefore, monometer is the appropriate label for a single-foot line of verse.