Which One of the Following Best Describes Progressive Discipline

Which one of the following best describes Progressive discipline?

A) Discussion of substandard performance, written warning, final written warning, termination.
B) Series of documents of employee's incompetence or insubordination that precedes an employee's termination.
C) Discussion of substandard performance, verbal warning, written warning, and final written warning.
D) Series of documents of employee's substandard performance prior to each step of discipline or termination.