**Core Concept**
The question is testing the student's knowledge of drugs that affect granulocyte migration. Granulocytes, including neutrophils and eosinophils, are a type of white blood cell that plays a crucial role in the immune response. Their migration towards sites of inflammation is essential for fighting infections. Certain drugs can inhibit this process, leading to impaired immune function.

**Why the Correct Answer is Right**
The correct answer is a drug that inhibits the action of chemokines, which are signaling molecules that attract granulocytes to sites of inflammation. The drug, **Corticosteroids**, specifically glucocorticoids, have anti-inflammatory properties that include the inhibition of granulocyte migration. This is achieved through the suppression of chemokine receptors on the surface of granulocytes, thereby reducing their ability to migrate towards inflammatory sites. Corticosteroids also reduce the production of chemokines, further inhibiting granulocyte migration.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specifically inhibit granulocyte migration. Instead, it may affect other aspects of immune function.
* **Option B:** This option is incorrect because it is not directly related to the inhibition of granulocyte migration. It may have other effects on the immune system.

**Clinical Pearl / High-Yield Fact**
Corticosteroids are commonly used to treat a variety of inflammatory conditions, including asthma, rheumatoid arthritis, and severe allergic reactions. They work by suppressing the immune system's response to inflammation, which can lead to a range of side effects, including increased susceptibility to infections.

**Correct Answer:** C. Corticosteroids.