How does Douglass put an end to Covey's brutal treatment of him?

AHe gets a root to carry in his right pocket to keep Covey from striking him.

BHe hides in a cornfield when Covey is seeking him to whip him.

CHe attacks Covey and beats him severely enough that Covey fears for his reputation as a slave-breaker.

DHe tries to work so well that Covey will have no reason to whip him.