How could you best describe the nature of an 'enigma'?

An 'enigma' refers to something that is mysterious, puzzling, or difficult to understand. The term often conveys a sense of complexity and unexpectedness, suggesting that there are layers of meaning or interpretation that are not immediately clear. This aligns perfectly with the choice that characterizes an enigma as puzzling and complex. Such a description captures the essence of what an enigma represents, which is typically an issue, scenario, or person that challenges our understanding or perception.

The other descriptions do not fit because they imply clarity or simplicity, which contradicts the fundamental quality of an enigma as something that is challenging and not easily decipherable. Therefore, the choice that describes an enigma as puzzling and complex accurately reflects its true nature.