**Core Concept**
Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis, which leads to decreased gastric mucosal protection and increased risk of gastric irritation and ulceration. Acetaminophen, although used for pain and fever, does not significantly inhibit COX enzymes and thus lacks anti-inflammatory action and minimal gastrointestinal side effects.

**Why the Correct Answer is Right**
Acetaminophen (paracetamol) acts primarily in the central nervous system and does not inhibit COX-1 or COX-2 in the gastrointestinal tract. Unlike NSAIDs such as diclofenac, ibuprofen, or naproxen, it does not interfere with prostaglandin production, which are essential for maintaining gastric mucosal integrity. Therefore, it causes minimal gastric irritation and is considered safer for the GI tract among analgesics.

**Why Each Wrong Option is Incorrect**
Option A: Diclofenac is a potent NSAID with strong COX-1 inhibition, leading to significant gastric irritation and ulcer risk.
Option C: Ibuprofen inhibits both COX-1 and COX-2, reducing gastric mucosal protection and increasing ulcer formation.
Option D: Naproxen, a long-acting NSAID, also suppresses COX-1, resulting in notable gastric side effects.

**Clinical Pearl / High-Yield Fact**
Acetaminophen is the only analgesic among common pain relievers that does not cause gastric irritation or ulcers, making it the preferred choice in patients with a history of peptic ulcer disease or gastrointestinal bleeding.

✓ Correct Answer: B. Acetaminophen