**Core Concept**
The concept of contributory negligence is a legal principle used in tort law to determine liability in cases where a plaintiff's actions contributed to their own injury or harm. This principle is essential in forensic medicine to assess the extent of responsibility in cases of medical malpractice or negligence.

**Why the Correct Answer is Right**
The avoidable consequences rule is a key component of contributory negligence. It states that a plaintiff cannot recover damages for injuries that were caused by their own actions, which they could have avoided by exercising reasonable care. This rule is based on the idea that individuals have a duty to take reasonable precautions to prevent harm to themselves. In the context of forensic medicine, the avoidable consequences rule is used to determine whether a patient's injuries were caused by their own negligence or by the actions of a healthcare provider.

**Why Each Wrong Option is Incorrect**
**Option A:** The eggshell skull rule refers to the principle that a defendant is liable for all damages resulting from an injury, even if the plaintiff has a pre-existing condition that makes them more susceptible to harm. This rule is unrelated to contributory negligence.

**Option B:** The master servant rule is a principle in tort law that holds a master (employer) liable for the actions of their servant (employee). This rule is not directly related to contributory negligence.

**Option D:** The common knowledge rule is not a recognized principle in forensic medicine or tort law. It is possible that this option is a distractor or a typo.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that contributory negligence is a defense that can be raised by a defendant to reduce their liability. Healthcare providers should be aware of this principle to ensure that they are taking reasonable precautions to prevent harm to their patients.

**✓ Correct Answer: C. Avoidable consequences rule. The avoidable consequences rule is a key component of contributory negligence, used to determine whether a patient's injuries were caused by their own negligence or by the actions of a healthcare provider.**