Final answer:
Option B, reviewing prior-year working papers and inquiring about changes, is the least effective method for internal auditors to learn about current laws and regulations as it relies on potentially outdated information and is not comprehensive.
Step-by-step explanation:
The internal auditors must determine the applicable laws and regulations. Among the listed procedures, reviewing prior-year working papers and inquiring of officials as to changes (option B) is generally considered the least effective method. This is because laws and regulations can change frequently, and relying solely on outdated information can result in the auditors not being aware of current compliance requirements.
While inquiring about changes can provide some updates, this approach lacks comprehensiveness and does not ensure that all current laws and regulations are accounted for. In contrast, reviewing applicable grant agreements (option A), making inquiries of the city's chief financial officer, legal counsel, or grant administrators (option C), and discussing the matter with the board and making inquiries as to the nature of the requirements and the board's objectives for the engagement (option D) are more proactive and likely to yield up-to-date information.