• Mechanism of Antiplatelet Action of Aspirin: Aspirin (acetylsalicylic acid) is a prototype antiplatelet drug that irreversibly inhibits platelet cyclooxygenase-1 (COX-1) via covalent acetylation of serine-529.
• Thromboxane Suppression: Platelets lack nuclei and cannot synthesize new enzyme; thus, aspirin permanently shuts down the synthesis of Thromboxane $A_2$ ($ ext{TXA}_2$), a potent platelet aggregator and vasoconstrictor, for the entire 7–10 day lifespan of circulating platelets.
• Other Options: While clopidogrel and ticlopidine are ADP-receptor blockers, aspirin remains the historical prototype antiplatelet agent.

Correct option: (1) Aspirin