Final answer:
Retirement of bonds payable is a capital expenditure.
Step-by-step explanation:
A capital expenditure refers to a long-term investment made by a company to acquire or improve its fixed assets, such as buildings, equipment, or vehicles, that will benefit the business over a longer period of time.
Among the given options, the only choice that represents a capital expenditure is b. Retirement of bonds payable. This is because retiring bonds payable involves the repayment of a long-term debt obligation, which is considered a capital expenditure.