## Core Concept
The question tests the understanding of sterilization methods for complex instruments and delicate materials. Sterilization is a critical process in healthcare to eliminate microbial life from surfaces, equipment, and supplies. Different methods are suited for various types of materials based on their heat sensitivity, complexity, and the level of sterility required.

## Why the Correct Answer is Right
The correct answer, **Low-temperature steam formaldehyde sterilization** or more commonly referred to in the context of complex and delicate equipment as **Ethylene Oxide (EO) sterilization** or **Hydrogen Peroxide Plasma Sterilization**, is favored for complex instruments and delicate materials. These methods are chosen because they can effectively sterilize heat-sensitive materials without damaging them. Ethylene oxide sterilization, for instance, works at a low temperature (usually around 37°C to 63°C), making it suitable for materials that cannot withstand high temperatures. Hydrogen peroxide plasma sterilization is another low-temperature method that is rapid and effective against a wide range of microorganisms.

## Why Each Wrong Option is Incorrect
- **Option A: Autoclaving** - This is a process that uses high-pressure steam to sterilize equipment. While highly effective for many types of medical instruments, it may not be suitable for delicate materials or complex instruments that are heat-sensitive or could be damaged by moisture.
- **Option B: Dry Heat Sterilization** - This method uses hot air to sterilize equipment. It is often used for materials that cannot get wet but can withstand high temperatures. However, it may not be ideal for complex or delicate instruments due to the high temperatures required and potential for uneven heating.
- **Option D: Radiation Sterilization** - While effective for certain types of medical supplies and equipment, radiation sterilization requires specialized facilities and is not commonly used for complex or delicate instruments that need to be reused immediately or are sensitive to radiation.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the choice of sterilization method depends on the material's compatibility with the method. For complex and delicate instruments, methods that are gentle (low temperature) and do not cause damage (such as moisture or radiation) are preferred. Ethylene oxide and hydrogen peroxide plasma sterilization are particularly valuable for such scenarios.

## Correct Answer: C. Low-temperature steam formaldehyde sterilization or more accurately for common practice: Ethylene Oxide (EO) sterilization or Hydrogen Peroxide Plasma Sterilization.