What does 'conundrum' refer to?

The term 'conundrum' refers to a complex problem, often one that is difficult to resolve or understand. It typically implies a situation or question that presents a challenge, requiring thought and consideration to figure out. This complexity can arise from various factors, such as contradictory information or the intricacies involved in the problem at hand. In contrast, a straightforward solution, an easy question, or a simple task suggest clarity and simplicity, which do not align with the notion of a conundrum. Thus, understanding 'conundrum' as a complex problem underscores the depth and challenge it presents, solidifying option C as the correct choice.