What is the primary mechanism of action of dexamethasone?

Dexamethasone is a potent corticosteroid. Its primary mechanism is inhibiting PHOSPHOLIPASE A2 (via lipocortin/annexin-1 induction), which prevents the release of arachidonic acid from membrane phospholipids — thereby blocking the production of BOTH prostaglandins AND leukotrienes. This is why it's more potent than NSAIDs (which only block COX). B (opioids), C (antihistamines), and D (cholinergics) describe other drug classes. A is correct.