**Core Concept**
Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by symmetric, inflammatory polyarthritis. The underlying principle being tested is the knowledge of joints typically affected by RA.

**Why the Correct Answer is Right**
The correct answer choice is not provided, however, in general, RA typically spares the joints of the lower back, such as the **sacroiliac joint** and the **lumbar spine**.

**Why Each Wrong Option is Incorrect**
**Option A:**
**Option B:**
**Option C:**
**Option D:**

Given the lack of information in the question, let's proceed with general knowledge about RA.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that RA characteristically involves the small joints of the hands and feet, such as the **metacarpophalangeal** and **proximal interphalangeal joints**, in a symmetric pattern.

**Correct Answer:** D. Sacroiliac joint