"Regulatory lag" refers to the period between the time when 

O a a firm is initially regulated by an agency and the time the firm "captures" that agency

 OD the natural monopolist changes its prices and the time when the regulatory agency rules on that change.

 C the regulatory agency decides to deregulate a firm and the timeout actually accomplishes the task

 d. the regulatory agency decides to regulate a firm and the time it actually accomplishes the task. e the natural monopolist's costs change and the time the regulatory agency adjusts the monopolist's prices