## Core Concept
Iridium-192 (Ir-192) is a radioactive isotope used in various medical and industrial applications, including brachytherapy for cancer treatment. Its half-life is crucial for determining the duration of its radioactive effects. The half-life of a radioactive substance is the time required for half of the initial amount of the isotope to decay.

## Why the Correct Answer is Right
The correct half-life of Iridium-192 is approximately 74 days. This duration makes Ir-192 suitable for medical applications, particularly in brachytherapy, where its radioactive properties can be utilized over a period that is long enough to treat tumors effectively but not so long that it poses prolonged risks. The half-life of 74 days allows for a controlled release of radiation.

## Why Each Wrong Option is Incorrect
- **Option A:** 10 days - This half-life is too short for Ir-192, which is known to have a longer duration of radioactivity.
- **Option B:** 14 days - Similarly, this is also too short and does not accurately represent the half-life of Ir-192.
- **Option D:** 365 days - This is too long and does not match the known half-life of Ir-192.

## Clinical Pearl / High-Yield Fact
A key point to remember is that Ir-192's half-life of approximately 74 days makes it a versatile tool in radiation therapy, allowing for the delivery of a precise dose of radiation to tumors over a controlled period. This characteristic is essential for its application in treating various cancers.

## Correct Answer Line
**Correct Answer: C. 74 days**