**Core Concept**
Filler particles are substances added to parenteral products to improve their appearance and facilitate their administration. They are designed to remain in the vial or syringe after the active pharmaceutical ingredient has been withdrawn, thereby preventing the loss of the drug and ensuring accurate dosing.

**Why the Correct Answer is Right**
The correct filler particle is a substance that does not interact with the active pharmaceutical ingredient and does not affect its stability or potency. In the context of parenteral products, filler particles are often made of materials such as lactose, glycine, or sodium chloride. These substances are inert and do not cause any adverse reactions when administered.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not a commonly used filler particle in parenteral products. While it may be used in other pharmaceutical applications, it is not a suitable filler particle for parenteral products.
**Option B:** This option is incorrect because it is a type of preservative, not a filler particle. Preservatives are added to parenteral products to prevent the growth of microorganisms, whereas filler particles are added to improve the appearance and facilitate the administration of the product.
**Option C:** This option is incorrect because it is a type of antifoaming agent, not a filler particle. Antifoaming agents are added to parenteral products to prevent foaming during preparation, whereas filler particles are added to improve the appearance and facilitate the administration of the product.

**Clinical Pearl / High-Yield Fact**
When selecting a filler particle for a parenteral product, it is essential to consider the compatibility of the filler particle with the active pharmaceutical ingredient and the preservative system. Incompatible filler particles can cause instability or degradation of the active ingredient, leading to reduced efficacy or safety of the product.

**Correct Answer: C.**