**Core Concept**
Injection thyroplasty is a minimally invasive surgical procedure used to treat vocal cord paralysis or weakness by injecting a material into the paralyzed vocal cord to improve voice quality. The choice of material is crucial in achieving optimal voice outcomes.

**Why the Correct Answer is Right**
The most commonly used materials for injection thyroplasty are calcium hydroxylapatite (CaHA) and autologous fat. Calcium hydroxylapatite is a biocompatible, non-resorbable material that provides long-lasting support to the vocal cord. Autologous fat, on the other hand, is a resorbable material that can provide temporary support to the vocal cord. The choice between these two materials depends on the patient's specific needs and the extent of vocal cord paralysis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a material commonly used for injection thyroplasty. While there may be other materials used in experimental or research settings, they are not standard choices for this procedure.
**Option B:** This option is incorrect because it is not a commonly used material for injection thyroplasty. While some materials may be used in other medical procedures, they are not typically used for this specific application.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the choice of material for injection thyroplasty should be based on the patient's specific needs and the extent of vocal cord paralysis. Calcium hydroxylapatite is generally preferred for more severe cases of vocal cord paralysis, while autologous fat may be used for milder cases.

**Correct Answer:** C. Calcium hydroxylapatite (CaHA) and autologous fat are the most commonly used materials for injection thyroplasty.