**Core Concept**
The extrinsic muscles of the tongue play a crucial role in its movement and function. These muscles attach the tongue to the surrounding bones and help in its elevation, depression, protrusion, and retraction. The extrinsic muscles responsible for depressing the tongue are of particular interest in this question.

**Why the Correct Answer is Right**
The extrinsic muscles that aid in depressing the tongue are the **genioglossus** and the **hyoglossus**. The genioglossus muscle originates from the mental spine of the mandible and inserts into the side of the tongue, while the hyoglossus muscle originates from the side of the body of the hyoid bone and inserts into the side of the tongue. Both of these muscles help in depressing the tongue by pulling it downwards. The **genioglossus** is the primary muscle responsible for this action, while the **hyoglossus** assists in this movement.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as it does not specify any muscle. The extrinsic muscles of the tongue are not the only muscles involved in its movement, but the question specifically asks for the extrinsic muscles that aid in depressing the tongue.
* **Option B:** This option is incorrect as it mentions the **styloglossus** muscle, which actually aids in retracting the tongue, not depressing it.
* **Option C:** This option is incorrect as it mentions the **digastric** muscle, which is not an extrinsic muscle of the tongue and does not aid in depressing the tongue.

**Clinical Pearl / High-Yield Fact**
It's essential to remember the extrinsic muscles of the tongue and their functions to avoid confusion in clinical scenarios. The genioglossus and hyoglossus muscles are key players in maintaining the airway and facilitating speech and swallowing.

**Correct Answer:** C.