**Core Concept**
The doctrine of res ipsa loquitur is a legal principle that applies to medical malpractice cases. It holds that certain injuries are so severe and unusual that they could not have occurred without negligence. This doctrine shifts the burden of proof from the plaintiff to the defendant, implying that the fact of the injury speaks for itself.

**Why the Correct Answer is Right**
The correct answer, "Fact speaks for itself," accurately reflects the essence of the doctrine. Res ipsa loquitur is a Latin phrase meaning "the thing speaks for itself." In medical malpractice cases, if a patient suffers an injury that would not have occurred without negligence, such as a retained foreign object or a perforated intestine, the court may infer negligence based on the nature of the injury itself. This doctrine is often applied when the medical treatment involved is so complex or unusual that it would be unreasonable to expect the patient to understand the risks involved.

**Why Each Wrong Option is Incorrect**
**Option A:** "Common knowledge" is not an accurate description of res ipsa loquitur, as it is a specific legal doctrine rather than a general concept.
**Option B:** "Medical maloccurance" is a vague term that does not capture the essence of the doctrine, which is focused on the inference of negligence from the nature of the injury.
**Option D:** "Oral evidence" is unrelated to the doctrine of res ipsa loquitur, which is based on the nature of the injury itself rather than the type of evidence presented.

**Clinical Pearl / High-Yield Fact**
The doctrine of res ipsa loquitur is often applied in cases involving retained foreign objects, such as surgical sponges or instruments, or in cases of perforated intestines or other severe injuries that could not have occurred without negligence.

**✓ Correct Answer: C. Fact speaks for itself**