## Core Concept
Plasma sterilization is a method used to eliminate microorganisms from medical instruments and equipment. The accuracy of this process is crucial to ensure patient safety. Assessing the effectiveness of plasma sterilization involves using a biological indicator.

## Why the Correct Answer is Right
The correct answer, **Biological indicators**, are used to assess the accuracy of plasma sterilization. Biological indicators contain highly resistant bacterial spores that are placed within the sterilization chamber. If the sterilization process is successful, these spores will be killed, indicating that the process was effective. This method provides a direct measure of the sterilization process's lethality.

## Why Each Wrong Option is Incorrect
* **Option A:** Chemical indicators change color in response to certain conditions of the sterilization process, such as temperature or the presence of a sterilizing agent, but they do not confirm the killing of microbial life.
* **Option B:** Physical indicators or monitors track parameters like temperature, pressure, or time during the sterilization process but do not directly assess microbial kill.
* **Option C:** This option seems to be missing but based on the context, any option suggesting chemical or physical indicators would be incorrect because they do not directly assess the effectiveness of sterilization.

## Clinical Pearl / High-Yield Fact
A key point to remember is that for processes like plasma sterilization, **biological indicators** are the gold standard for validating the effectiveness of the sterilization process. This is because they directly measure the process's ability to kill microbial life, which is the ultimate goal of sterilization.

## Correct Answer Line
**Correct Answer: D. Biological indicators.**