Which event must be disclosed by issuers under SEC rules?

The correct choice is based on the requirement that issuers must disclose any material changes in their financial condition under SEC rules. This obligation ensures transparency and provides investors with critical information that could affect their decision-making regarding the purchase or sale of securities. Material changes could include significant alterations in revenue, expenditures, or overall financial health that may impact the issuer's ability to meet its debt obligations.

This requirement is pivotal for maintaining market integrity and investor confidence, as the financial health of an issuer is a key factor in assessing risk. The SEC has set these disclosure guidelines to protect investors and ensure they have access to relevant information in a timely manner.

In contrast, the other options do not constitute mandatory disclosures under SEC rules for issuers. Routine budget approvals, while important for internal management, do not typically have the same level of impact or materiality that would affect investor decisions directly. Changes in local ordinances and the approval of new municipal projects may also be significant but do not always rise to the level of material changes in financial condition that require disclosure under SEC regulations. Thus, the focus on material changes roots the requirement in the need for transparency regarding factors that could significantly influence an issuer's financial stability and associated risks.