Final answer:
Mannose-binding lectin (MBL) is a pattern recognition receptor that activates the lectin pathway of the complement system. However, it is not produced by B lymphocytes.
Step-by-step explanation:
The correct answer is (D) It is produced by B lymphocytes.
Mannose-binding lectin (MBL) is a pattern recognition receptor (PRR) that activates the lectin pathway of the complement system when it binds to carbohydrates on pathogens. It is primarily synthesized by the liver and secreted into the bloodstream as an acute-phase protein during an immune response. Unlike antibodies, MBL is not produced by B lymphocytes.