Final answer:
The most severe penalty a board may impose is c) License revocation, which is considered a formal negative sanction and prohibits an individual from legally practicing their profession.
Step-by-step explanation:
The most severe penalty a board may impose on a professional for violations of rules, standards, or practices is generally c) License revocation. This action falls under the category of formal negative sanctions, which are actions taken by a body or institution to penalize an individual for non-compliance to norms or regulations.
A license revocation strips the individual of their professional credentials, effectively prohibiting them from legally practicing their profession. This is more severe than other penalties such as a fine, probation, or a written warning, as it represents a complete cessation of one's professional status, often making it very difficult to regain the license in the future.