**Core Concept**
Alteplase and streptokinase are both thrombolytic agents used to dissolve blood clots. They work by activating plasminogen to plasmin, which then degrades fibrin in the clot, restoring blood flow. The key difference lies in their mechanism of action and administration.

**Why the Correct Answer is Right**
Alteplase is a recombinant tissue plasminogen activator (tPA) that specifically binds to fibrin in the clot, activating plasminogen to plasmin. This results in a more targeted and efficient clot lysis. In contrast, streptokinase is a non-specific activator of plasminogen, which can lead to systemic activation of plasminogen and increased bleeding risk. Alteplase also has a more predictable dose-response curve, making it a safer option in certain clinical scenarios.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because alteplase and streptokinase have different mechanisms of action, but this is not the correct difference being asked.
**Option B:** This option is not provided, so we cannot explain why it is incorrect.
**Option C:** This option is incorrect because the half-life of alteplase is not the key difference between the two drugs.
**Option D:** This option is not provided, so we cannot explain why it is incorrect.

**Clinical Pearl / High-Yield Fact**
When choosing between alteplase and streptokinase, consider the patient's risk of bleeding, the site of the clot, and the time elapsed since symptom onset. Alteplase may be preferred in acute ischemic stroke, pulmonary embolism, or when a more targeted clot lysis is desired.

**Correct Answer: A. Alteplase is a recombinant tissue plasminogen activator (tPA) that specifically binds to fibrin in the clot, whereas streptokinase is a non-specific activator of plasminogen.**