**Core Concept**
The underlying principle being tested is the method of sterilization for disposable plastic syringes, focusing on the most effective and suitable technique for this specific material. **Gamma radiation** is a key concept in this context, as it is widely used for sterilizing medical devices.

**Why the Correct Answer is Right**
Gamma radiation is the correct answer because it is a highly effective method for sterilizing disposable plastic syringes without damaging the material. This method uses **ionizing radiation** to kill bacteria and other microorganisms, ensuring the syringes are safe for use. Gamma radiation penetrates deeply, allowing for the sterilization of packaged items.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while **autoclaving** is a common sterilization method, it may not be suitable for all types of plastic syringes due to the high temperatures and pressures involved.
**Option B:** This option is incorrect because **ethylene oxide sterilization** is used for heat-sensitive materials but has its own set of limitations and requirements.
**Option D:** This option is incorrect as it is not specified, but generally, other methods like **dry heat** are less effective for plastic materials.

**Clinical Pearl / High-Yield Fact**
Remember, gamma radiation is ideal for sterilizing disposable plastic syringes due to its penetrating power and effectiveness against a wide range of microorganisms. This method is crucial for ensuring patient safety by preventing infections.

**Correct Answer:** D. Gamma Radiation.