**Core Concept**
A ranula is a type of mucocele that occurs in the floor of the mouth, typically resulting from the obstruction of the sublingual gland or duct. This condition is characterized by the accumulation of mucin, leading to a translucent, bluish swelling.

**Why the Correct Answer is Right**
Ranulas are usually associated with the sublingual gland or duct, rather than the submandibular gland. The sublingual gland is a major salivary gland located under the tongue, and its duct opens into the floor of the mouth. Obstruction of this duct or gland can lead to the formation of a ranula. The incorrect association with the submandibular gland, which is another major salivary gland located in the submandibular triangle, is a common confusion.

**Why Each Wrong Option is Incorrect**
**Option A:** A retention cyst is a type of cyst that forms due to the obstruction of a gland or duct, which is indeed true for ranulas. They result from the accumulation of mucin due to ductal obstruction.
**Option C:** Ranulas are typically translucent and bluish due to the presence of mucin, which is correct. This characteristic is often used in clinical diagnosis.
**Option D:** Plunging ranula is a variant of ranula where the mucin collection extends into the neck, forming a submandibular or submental swelling. This is a recognized feature of ranulas.

**Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that ranulas are often associated with a history of trauma or surgery in the floor of the mouth, which can lead to ductal obstruction and mucin accumulation. It is essential to investigate for any underlying cause of the obstruction.

**✓ Correct Answer: B. Arises from submandibular gland**