If, in response to a complaint, Lin denies that she is responsible for Martino's harms, and further, that Martino actually caused harm to her, what is this called?

counterclaim

Explanation:

counterclaim is defensive process in which person or party  made opposing claim. If one party file case against other it is called claim and if other party file case against first party to offset claim it is known as counterclaim. i-e if company A file claim that company B fraud in contract it is known as claim and similarly if company B files claim that Company A is responsible and made fraud it is known as counterclaim in legal action.

they all focused on themes about the inevitability of death.

answer; eliminate parking problems in cities, because a car took up only half as much space as a horse and buggy;