**Core Concept**
The maximum permissible dose of radiation is a critical limit set by regulatory agencies to ensure the safety of individuals exposed to ionizing radiation, such as medical professionals operating X-ray machines. This concept is based on the principle of minimizing radiation-induced harm to workers, with the goal of preventing deterministic effects and limiting stochastic effects to a low probability.

**Why the Correct Answer is Right**
The maximum permissible dose of radiation is set at 50 millisieverts (mSv) per year, averaged over a 5-year period, for workers in the medical field. This limit is established by the International Commission on Radiological Protection (ICRP) and is enforced by regulatory agencies worldwide. The dose limit is designed to protect workers from the stochastic effects of radiation, such as cancer and genetic damage, while also accounting for the potential for deterministic effects, such as radiation burns and acute radiation syndrome, at higher doses.

**Why Each Wrong Option is Incorrect**
* **Option A:** There is no established maximum permissible dose of radiation for workers in the medical field at 25 mSv per year. While this dose may be below the limit, it is not the maximum permissible dose.
* **Option B:** 100 mSv per year is above the maximum permissible dose for workers in the medical field and would increase the risk of radiation-induced harm.
* **Option D:** There is no established maximum permissible dose of radiation for workers in the medical field at 200 mSv per year. This dose is significantly above the recommended limit and would pose a serious risk to worker safety.

**Clinical Pearl / High-Yield Fact**
The maximum permissible dose of radiation is a critical limit that varies depending on the occupation and the type of radiation exposure. Medical professionals should be aware of their individual dose limits and take steps to minimize their radiation exposure to ensure safe working practices.

**Correct Answer:** C. 50 mSv.