**Core Concept**
Cyclo-oxygenase-1 (COX-1) is an enzyme responsible for the conversion of arachidonic acid to prostaglandin H2, playing a crucial role in maintaining normal gastric mucosal function and platelet aggregation.

**Why the Correct Answer is Right**
COX-1 isoenzyme is constitutively expressed in most tissues, including the stomach lining, and is involved in the synthesis of prostaglandins that help protect the gastric mucosa from acid-induced damage. It is also responsible for the production of thromboxane A2 in platelets, which promotes platelet aggregation and vasoconstriction. The selective inhibition of COX-1 isoenzyme by nonsteroidal anti-inflammatory drugs (NSAIDs) leads to the reduction of gastric mucosal protection and an increased risk of gastrointestinal side effects.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately describe the primary function of COX-1. COX-2 isoenzyme is primarily involved in the production of prostaglandins in response to inflammation and is not constitutively expressed.
**Option B:** This option is incorrect as it does not accurately describe the role of COX-1 in platelet aggregation. COX-1 is involved in the production of thromboxane A2, which promotes platelet aggregation, but this is not its primary function.
**Option C:** This option is incorrect as it does not accurately describe the mechanism of action of COX-1 inhibitors. COX-1 inhibitors work by selectively inhibiting the COX-1 isoenzyme, leading to a reduction in prostaglandin synthesis and an increased risk of gastrointestinal side effects.

**Clinical Pearl / High-Yield Fact**
The use of selective COX-2 inhibitors has been associated with a reduced risk of gastrointestinal side effects compared to non-selective NSAIDs, but may increase the risk of cardiovascular events.

**Correct Answer: B. It is involved in platelet aggregation.**