**Core Concept**
Streptokinase is a thrombolytic agent that works by activating the fibrinolytic system, leading to the breakdown of fibrin clots and restoration of blood flow. However, its use is associated with several complications due to its potent fibrinolytic activity and potential to trigger an immune response.

**Why the Correct Answer is Right**
The correct answer is related to the bleeding complications associated with streptokinase, as it can cause systemic fibrinolysis, leading to bleeding from various sites, including gastrointestinal, intracranial, and retroperitoneal spaces. This is because streptokinase activates plasminogen to plasmin, which then degrades fibrin and other clotting factors, increasing the risk of bleeding.

**Why Each Wrong Option is Incorrect**
**Option A:** Hypersensitivity reactions are a potential complication of streptokinase, but they are not the most common or severe complication.
**Option B:** Fever is a possible side effect of streptokinase, but it is not a direct complication of the medication.
**Option C:** Hypotension can occur with streptokinase due to its vasodilatory effects, but it is not a primary complication of the medication.

**Clinical Pearl / High-Yield Fact**
Streptokinase should be used with caution in patients with a history of bleeding disorders or those taking anticoagulant medications, as it can increase the risk of severe bleeding.

**Correct Answer:** A. Bleeding complications.