**Core Concept**
Rheumatoid arthritis (RA) and Systemic Lupus Erythematosus (SLE) are both autoimmune diseases that can present with polyarthritis. However, they have distinct clinical features and laboratory markers that help in differentiating between the two conditions.

**Why the Correct Answer is Right**
The presence of **deposits of immunoglobulins and complement on renal biopsy** is a characteristic feature of SLE and is not typically seen in RA. This is due to the deposition of immune complexes in the kidneys, which leads to inflammation and damage. In contrast, RA is characterized by the presence of **rheumatoid factor (RF) and anti-CCP antibodies**, which are autoantibodies that target the Fc region of IgG and are highly specific for RA.

**Why Each Wrong Option is Incorrect**
**Option A:** Presence of morning stiffness, which is a common feature of both RA and SLE. While morning stiffness is a characteristic feature of RA, it is also seen in SLE, making it a non-specific feature for differentiating between the two conditions.
**Option B:** Elevated ESR and CRP levels, which are non-specific markers of inflammation and are seen in both RA and SLE.
**Option C:** Presence of photosensitivity, which is a characteristic feature of SLE but can also be seen in RA.

**Clinical Pearl / High-Yield Fact**
In differentiating between RA and SLE, it is essential to look for specific laboratory markers and clinical features, rather than relying on non-specific symptoms such as morning stiffness and photosensitivity.

**Correct Answer: D. Deposits of immunoglobulins and complement on renal biopsy.**