**Core Concept**
The question is testing the knowledge of salivary gland function and the relative contribution of each gland to total saliva production. The parotid, submandibular, and sublingual glands are the three major salivary glands in the human body.

**Why the Correct Answer is Right**
The submandibular gland secretes a significant amount of saliva, which is rich in amylase, an enzyme that breaks down carbohydrates. The submandibular gland's saliva makes up more than half of the total saliva secreted by all the salivary glands in a day. This is because the submandibular gland has a higher secretory capacity and a more significant contribution to the mixed saliva, which is the primary type of saliva that comes into contact with food during mastication.

**Why Each Wrong Option is Incorrect**
* **Option A:** The parotid gland is the largest salivary gland but contributes less to the total saliva production compared to the submandibular gland.
* **Option B:** The sublingual gland produces a small amount of mucinous saliva, which makes up a minor portion of the total saliva secreted by all the salivary glands.
* **Option D:** The minor salivary glands, which are scattered throughout the oral cavity, contribute a small amount of saliva to the total production.

**Clinical Pearl / High-Yield Fact**
The submandibular gland's saliva is rich in amylase, which is essential for carbohydrate digestion. Impaired submandibular gland function can lead to reduced amylase activity, resulting in carbohydrate malabsorption.

**Correct Answer:** C. The submandibular gland secretes more than half of the total amount of saliva secreted by all the salivary glands in a day.