What characterizes something described as "grueling"?

Describing something as "grueling" indicates that it is extremely challenging and exhausting, often requiring a great deal of effort and endurance. This term frequently refers to tasks or activities that are physically or mentally taxing, leaving individuals feeling fatigued and worn out after completion. The nature of a grueling task implies a level of difficulty that can lead to exhaustion, whether it be due to the demands placed upon an individual or the intensity of the activity involved.

In contrast, the other options describe scenarios that lack this level of difficulty or exertion. A mundane process suggests a lack of engagement or challenge; a simple activity indicates ease and low pressure; and an engaging competition with minimal challenges implies excitement but without the rigorous demands that characterize something grueling. Thus, the accurate portrayal of "grueling" aligns perfectly with the notion of a challenging task that is exhausting.