Which of the following best describes the crime committed by the municipal official?

The scenario describes a local municipal official sharing confidential information about planned infrastructure repairs with "the mafias." This information allows the mafias to damage the infrastructure before it is fixed, and the official receives a personal benefit for this action.

Let's analyze the options:

• a. Institutional crime, because the official used his or her institutional position to benefit the mafia network. While the official does use their institutional position, "institutional crime" typically refers to crimes committed by or on behalf of an institution, or where the institution's structure facilitates the crime. Here, an individual within the institution is collaborating with an external criminal group. This is a form of corruption, which can be related to institutional failings, but "organized crime" better describes the collaborative nature.
• b. Organised crime, because the official is working as part of the broader mafia network rather than acting alone. This option accurately captures the essence of the crime. Organized crime involves structured groups of people engaged in illegal activities, often for profit, and frequently involves corruption of public officials to facilitate their operations. The official is not acting alone but is an integral part of a scheme involving "the mafias," which are by definition an organized criminal network. The official's actions directly support and benefit this network.
• c. This is not a financial crime, because the official is not directly involved in damaging the infrastructure. This is incorrect. The official receives a "benefit" (financial gain) for sharing information, making it a financial crime. Facilitating a crime for profit is still a financial crime, regardless of direct physical involvement in every aspect.
• d. Tax evasion, because the official receives a payment for the information, and this payment will likely not be declared for tax purposes. While the official might also be committing tax evasion by not declaring the illicit payment, the primary crime described is the act of corruption and collaboration with a criminal network to facilitate damage for profit. Tax evasion is a specific type of financial crime related to taxes, not the overarching criminal activity described.

The most fitting description is organized crime because the official is actively collaborating with a "mafia network" to achieve criminal objectives for mutual financial benefit.

The final answer is $\boxed{\text{b}}$