**Core Concept**
Disease-Modifying Antirheumatic Drugs (DMARDs) are a class of medications used to treat rheumatoid arthritis and other autoimmune diseases. They work by modifying the course of the disease and reducing inflammation, rather than just relieving symptoms.

**Why the Correct Answer is Right**
The correct answer is a DMARD because it targets the underlying pathophysiology of autoimmune diseases, such as rheumatoid arthritis. DMARDs often work by inhibiting the production of cytokines, which are signaling molecules that promote inflammation. For example, methotrexate, a commonly used DMARD, works by inhibiting the enzyme dihydrofolate reductase (DHFR), which is involved in the synthesis of purines and pyrimidines. This leads to a decrease in the production of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha).

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a corticosteroid, which is a type of immunosuppressive medication that relieves symptoms but does not modify the underlying disease process.
**Option B:** This option is incorrect because it is a biologic agent, which is a type of medication that targets specific molecules involved in inflammation, but it is not a DMARD.
**Option C:** This option is incorrect because it is a nonsteroidal anti-inflammatory drug (NSAID), which is a type of medication that relieves pain and inflammation, but does not modify the underlying disease process.

**Clinical Pearl / High-Yield Fact**
DMARDs should be started early in the treatment of rheumatoid arthritis, as they can help slow disease progression and improve long-term outcomes.

**Correct Answer: C. Hydroxychloroquine**