Final answer:
Option (c), Caitlin should use the operating account specific to the unit for routine maintenance expenses, as it's meant for day-to-day expenses related to property upkeep.
Step-by-step explanation:
For routine maintenance of an apartment complex unit, Caitlin should use the operating account for that specific unit. The operating account is intended for the day-to-day expenses associated with the property, including maintenance and repairs.
Trust accounts, on the other hand, are typically used to hold tenant deposits or to keep client funds separate for legal or contractual reasons. Therefore, option c, the operating account for that specific unit, would be the correct bank account to use for such expenses.