Okay, let's tackle this question. The question is about the lining of the parietal peritoneum. Hmm, I remember that the peritoneum has two layers: the parietal and the visceral. But what lines them?

Wait, the parietal peritoneum is the outer layer, covering the abdominal wall. I think both the parietal and visceral are lined by mesothelium. Mesothelium is a type of epithelium, right? It's a simple squamous epithelium. So the answer should be simple squamous epithelium. But let me make sure.

Wait, sometimes people confuse it with endothelium or other types. The visceral peritoneum, which is the inner layer covering the organs, is also lined by mesothelium. So both layers are made of the same type of epithelium. The options might have other epithelial types like stratified or transitional. Let me check the options again. The user didn't list the options, but typical distractors could be pseudostratified, stratified, or maybe even a mix-up with other tissues.

So the correct answer is simple squamous epithelium. The wrong options would be other epithelial types. For example, if an option says "stratified squamous," that's incorrect because the peritoneum is not exposed to abrasion, so it doesn't need stratified. Similarly, transitional epithelium is in the urinary system, not peritoneum. Pseudostratified is found in the respiratory tract. So the key here is remembering that both parietal and visceral peritoneum are lined by simple squamous epithelium called mesothelium.

**Core Concept**
The parietal peritoneum is a serous membrane lining the abdominal cavity wall. It is composed of **simple squamous epithelium (mesothelium)** and a thin layer of connective tissue. This lining is identical to the visceral peritoneum covering abdominal organs.

**Why the Correct Answer is Right**
The parietal peritoneum is lined by **simple squamous epithelium (mesothelium)**, which secretes serous fluid to reduce friction between peritoneal surfaces during organ movement. Mesothelium is a specialized epithelium derived from mesoderm, distinct from endothelium (lining blood vessels) or other epithelial types. Its single-cell layer ensures minimal resistance to fluid exchange and motility.

**Why Each Wrong Option is Incorrect**
**Option A:** *Stratified squamous epithelium* is found in areas requiring mechanical protection (e.g., skin), not in the peritoneal cavity.
**Option B:** *Pseudostratified epithelium* lines the respiratory tract, not serous membranes.
**Option C:** *Transitional epithelium* is found in the urinary system (e.g., bladder), allowing distension.

**Clinical Pearl / High-Yield Fact**
Remember: **Mesothelium (simple squamous)** lines all serous cavities (peritoneal, pleural, pericardial). Confusion with **endothelium** (simple squamous lining blood vessels) is common in exams—focus on anatomical location.

**Correct Answer: D. Simple squamous epithelium**

✓ Correct Answer: A. Simple squamous