Which word describes something that is 'extended in time'?

The word that describes something as "extended in time" is protracted. This term specifically refers to situations or periods that are prolonged or drawn out over a longer duration than necessary or expected. For example, a protracted negotiation suggests that the discussions have taken much longer than anticipated.

The other choices do not convey the notion of duration. Onerous suggests a burden or something that is oppressive or burdensome rather than time-related. Composite refers to something made up of various parts or elements, which does not relate to the idea of time. Ephemeral means lasting for a very short time, directly opposing the idea of being extended in time. Thus, protracted is the most fitting term for describing something that is extended in duration.