**Core Concept**
The submandibular gland is a major salivary gland that plays a crucial role in the production and secretion of saliva. It is a mixed gland, consisting of both serous and mucous acini, and has a complex ductal system that facilitates the transport of saliva into the oral cavity.

**Why the Correct Answer is Right**
The correct answer is one of the options listed below. To determine which one is incorrect, let's examine each option in relation to the submandibular gland.

**Why Each Wrong Option is Incorrect**
**Option A:**
The submandibular gland is indeed a mixed gland, consisting of both serous and mucous acini. This characteristic is a key feature of the gland's function and structure.

**Option B:**
The submandibular gland is responsible for producing a significant portion of the total saliva produced in the oral cavity. This is due to its large size and complex ductal system.

**Option C:**
The Wharton's duct is the main excretory duct of the submandibular gland, which opens into the oral cavity near the second molar tooth. This is a critical anatomical feature of the gland.

**Option D:**
The submandibular gland is primarily innervated by the chorda tympani nerve, which carries preganglionic parasympathetic fibers from the otic ganglion. This is a critical aspect of the gland's innervation and function.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the submandibular gland is often involved in cases of sialolithiasis, a condition characterized by the formation of stones within the gland's ductal system. This can lead to significant pain and swelling in the region.

**Correct Answer:** D.