Which of the following best illustrates a change order?

A change order is a formal document that modifies specific contractual obligations within a contract. This typically involves changes to the scope of work, price adjustments, or an extension of the timeline. By defining the alterations clearly, a change order ensures both parties have a mutual understanding of the adjustments being made to the contract.

The other options do not represent change orders clearly. An informal request for change lacks the formal documentation required to modify the existing contract terms. A notice of delay in performance could impact timelines but does not imply a modification to the actual contractual obligations. Lastly, an extension of time due to unforeseen circumstances might be related to changes in schedule but does not encompass the broader modifications in scope or terms that a change order typically includes.