Pinker Proposes That in Order to "Morph" Words into Different

Pinker proposes that in order to "morph" words into different forms (i.e. ,past tense) ,we have

A) one system that is associative;we encode associations between the past and present tense and use them to retrieve one another.
B) one system that operates via rules;we use these rules (e.g. ,"add an -s to make a plural") to morph words.
C) two systems;we use the rule system for exceptions and the associative system for non-exceptions.
D) two systems;we use the rule system for non-exceptions and the associative system for exceptions.