**Core Concept**
Phospholipids are a class of lipids that contain a hydrophilic (water-loving) head group and a hydrophobic (water-fearing) tail group. They are a crucial component of cell membranes and play a vital role in various cellular processes. Glycerol is a key component of most phospholipids, serving as the backbone to which the fatty acid chains and phosphate groups are attached.

**Why the Correct Answer is Right**
Phospholipids that do not contain glycerol are known as sphingophospholipids or sphingolipids. These molecules have a different structure, with a sphingosine backbone instead of glycerol. Sphingophospholipids are a distinct class of phospholipids that are found in cell membranes and are involved in various cellular processes, including cell signaling and membrane trafficking.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because glycerophospholipids, such as phosphatidylcholine, contain glycerol as their backbone.
* **Option B:** This option is incorrect because glycerophospholipids, such as phosphatidylethanolamine, contain glycerol as their backbone.
* **Option D:** This option is incorrect because glycerophospholipids, such as phosphatidylinositol, contain glycerol as their backbone.

**Clinical Pearl / High-Yield Fact**
Sphingolipids are a unique class of phospholipids that are involved in various cellular processes, including cell signaling and membrane trafficking. They are also a key component of myelin, the fatty substance that surrounds and protects nerve fibers.

**Correct Answer: C. Sphingolipids. Sphingolipids are a class of phospholipids that do not contain glycerol.**