Final answer:
An exception to the doctrine of employment at will is an implied contract, where the employer's actions or policies create the expectation that employees will not be fired without cause. Option C is correct.
Step-by-step explanation:
An exception to the doctrine of employment at will is c. Implied contract. This refers to a situation where an employer's policies or actions create a reasonable expectation by the employee that they will not be fired without cause. Examples of where an implied contract could be found include an employer providing a handbook stating that employees will only be terminated for cause or a history of the company only terminating employees for cause, leading employees to believe that they too will only be terminated for the same reasons. This is contrary to a probationary period where the employer retains the right to dismiss an employee without cause during a specific timeframe.