Joe Michaelson, a sales representative who has been with the York Corporation for $15$ years, was shocked when the company suddenly informed him that he had been terminated and did not provide any reason for the decision. The employer acted within its rights based on the employment$-$at$-$will concept which

A$.$ has become more influential in recent years.

B$.$ has more legal consequences in voluntary turnover than in involuntary turnover.

C$.$ implies that a person may leave an organization at will despite an existing contract.

D$.$ allows employers to discharge people despite an existing contract.

E$.$ states that in the absence of a specific contract, either party could sever the employment.