**Core Concept**
Ludwig's angina is a severe infection of the submandibular space, characterized by rapid progression and potential airway compromise. It typically involves the submandibular and sublingual spaces, which are located below the mylohyoid muscle.

**Why the Correct Answer is Right**
Involvement of the 2nd premolar and 1st molars in Ludwig's angina indicates that the infection is spreading from the submandibular space to the sublingual space. The first involved space is the sublingual space, as the 2nd premolar and 1st molars are located near the anterior border of the sublingual space. The sublingual space is a potential space located below the mylohyoid muscle and above the submandibular space, which is often involved in Ludwig's angina.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as the submandibular space is often involved in Ludwig's angina, but the question asks for the first involved space, which is the sublingual space.
* **Option B:** This option is incorrect as the submental space is a separate space located below the chin and is not directly involved in the spread of infection from the submandibular space.
* **Option D:** This option is incorrect as the submaxillary space is an older term for the submandibular space, which is often involved in Ludwig's angina.

**Clinical Pearl / High-Yield Fact**
Remember the submandibular space is often involved in Ludwig's angina, but the sublingual space is the first involved space when the 2nd premolar and 1st molars are involved.

**Correct Answer:** C.