## Core Concept
Inquest is a judicial inquiry in common law jurisdictions that determines the cause of a person's death. It is typically conducted when a death occurs under suspicious, unexpected, or violent circumstances. The primary goal is to ascertain the cause and circumstances of death.

## Why the Correct Answer is Right
The correct answer, **C. Judicial inquiry to ascertain cause of death**, accurately reflects the definition and purpose of an inquest. An inquest involves a legal process where a coroner or a jury examines the facts surrounding a death to determine its cause. This process helps in ensuring that if a death was unnatural or suspicious, it is thoroughly investigated.

## Why Each Wrong Option is Incorrect
- **Option A:** "Magistrate's order for postmortem" - This option is incorrect because while a postmortem examination might be part of an inquest, the inquest itself is a broader judicial process aimed at determining the cause of death, not just an order for a postmortem.
- **Option B:** "Police inquiry into a crime" - This option is incorrect because, although an inquest may sometimes overlap with police inquiries, it is specifically focused on determining the cause of death rather than investigating a crime in general.
- **Option D:** "Doctor's opinion on cause of death" - This option is incorrect because, while a doctor's opinion (often through a postmortem report) may be crucial in an inquest, the inquest itself is a legal process that goes beyond just a doctor's opinion.

## Clinical Pearl / High-Yield Fact
A key point to remember is that an inquest is crucial in cases of suspicious or unexpected deaths, as it provides a formal process for investigating the circumstances and cause of death. This process can have significant implications for public health, legal proceedings, and the families of the deceased.

## Correct Answer: C. Judicial inquiry to ascertain cause of death