**Core Concept:**
Seronegative spondyloarthritis refers to a group of inflammatory arthritis conditions characterized by back pain and inflammation of the spine and peripheral joints, but without positive rheumatoid factor or anti-citrullinated protein antibodies (ACPA). Treatment focuses on relieving symptoms and slowing down the disease progression.

**Why the Correct Answer is Right:**
The correct answer is **D**: Nonsteroidal anti-inflammatory drugs (NSAIDs) are the first-line treatment option for seronegative spondyloarthritis. They help in reducing inflammation, pain, and stiffness. Examples include ibuprofen and naproxen.

**Why Each Wrong Option is Incorrect:**

A. **Option A (Glucocorticoids):** These are potent anti-inflammatory and immunosuppressive agents. However, their use is limited due to potential side effects like osteoporosis, infections, and adrenal suppression.

B. **Option B (Biologic agents):** These are advanced immunosuppressive drugs targeting specific immune system components like tumor necrosis factor (TNF) or interleukin-17. Although effective, they require careful monitoring due to increased risk of infections and malignancies.

C. **Option C (Physiotherapy and exercise):** While these non-pharmacological interventions are essential for maintaining mobility, they are not sufficient as a sole treatment for seronegative spondyloarthritis.

**Clinical Pearl:**
In seronegative spondyloarthritis, early management with NSAIDs can help improve disease outcomes, reduce pain, and maintain joint function. Physiotherapy and exercise should be combined with pharmacological treatment.

**Correct Answer:** D: Nonsteroidal anti-inflammatory drugs (NSAIDs) serve as the first-line treatment option due to their effectiveness in managing symptoms and reducing inflammation without the severe side effects of glucocorticoids or biologic agents.