Which of the following is not a common law defense?

The concept of comparative negligence is a legal doctrine that allows for the apportionment of fault among parties involved in an accident or injury. It modifies the traditional common law doctrine of contributory negligence, which completely bars a plaintiff from recovery if they are found to have any degree of fault in an incident. Comparative negligence, on the other hand, permits a plaintiff to recover damages even if they are partially at fault, reducing their award based on their percentage of fault.

The other options listed—contributory negligence, assumption of risk, and last clear chance—are all traditional common law defenses that originated in case law and have been used in various jurisdictions. Contributory negligence denies recovery to a plaintiff if they contributed in any way to their injury, assumption of risk involves acknowledging and accepting the dangers associated with an activity, and last clear chance provides a means for a plaintiff to recover damages if the defendant had the final opportunity to avoid the harm. Since comparative negligence does not fall under the classic common law framework and instead reflects more modern approaches to tort law, it stands out as not being a traditional common law defense.