Answer :
It is C. It is C because it uses specific lexical or syntactical elements that are not considered to be the standard. This is a Pirate dialect, and people who are not pirates, or weren't pirates at that time, couldn't understand what a "shirking lubber". You were correct when you said "normal" because normal in this sense means that it is a grammatically correct standardized version of English.
C. "'Search him, some of you shirking lubbers, and the rest of you aloft and get the chest,' he cried."