Final answer:
IgA (Immunoglobulin A) (option B) is the second most abundant Immunoglobulin in plasma, key to mucosal immunity, and is predominantly found in bodily secretions like saliva and tears.
Step-by-step explanation:
The second most abundant Immunoglobulin in the plasma is IgA (Immunoglobulin A). While IgG is the most prevalent, accounting for about 80% of total serum antibodies and providing a broad range of defense mechanisms such as crossing the placental barrier and activating complement proteins, IgA stands as the second largest class with its significant presence in protective bodily secretions. IgA is crucial for mucosal immunity as it is found in seromucous secretions like saliva, tears, respiratory and gastrointestinal secretions, and provides protection against microbial invasion.