**Core Concept**
Bence-Jones proteinuria refers to the excretion of free light chains in the urine, which are immunoglobulin fragments produced by plasma cells. These light chains are derived from the immunoglobulin light chains (kappa or lambda) and are typically seen in multiple myeloma and other plasma cell dyscrasias.

**Why the Correct Answer is Right**
Bence-Jones proteins are monomeric light chains of immunoglobulins, specifically the free kappa or lambda chains, released by abnormal plasma cells. These light chains are not part of intact immunoglobulins but are secreted into the blood and filtered by the kidneys, leading to their appearance in urine. The presence of these light chains in urine is a hallmark of plasma cell disorders.

**Why Each Wrong Option is Incorrect**
Option A: Alpha globulins are primarily composed of albumin and other proteins, not light chains, and are not associated with Bence-Jones proteinuria.
Option C: Gamma globulins are intact immunoglobulins (e.g., IgG, IgA), not free light chains, and are not the source of Bence-Jones proteins.
Option D: Delta globulins are minor components of serum immunoglobulins and are not linked to Bence-Jones proteinuria.

**Clinical Pearl / High-Yield Fact**
Bence-Jones proteinuria is a key diagnostic clue in multiple myeloma and other plasma cell dyscrasias; it appears as an unpaired, low-molecular-weight protein in urine and can be detected by electrophoresis or immunoassays.

✓ Correct Answer: B. Light chain globulins