What is the meaning of the term 'onerous'?

The term 'onerous' refers to something that is burdensome or involved in hardship and difficulty. It describes obligations or tasks that require considerable effort or that are excessively demanding, often resulting in a sense of strain. When someone describes a duty or job as onerous, they are highlighting the discomfort or challenge associated with fulfilling it. This aligns seamlessly with the definition provided in the correct choice.

The other definitions, while they describe different characteristics, do not capture the essence of 'onerous.' For instance, something that is short-lived, instructive, or extended in time does not convey the heaviness or challenging nature implied by the word 'onerous.' Thus, the correct answer effectively encapsulates the primary meaning of the term.