This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
A 50 year old female patient complains of weakness and pain in back. Patient gives history of recurrent infections. Lab investigation reveals presence of Bence Jones proteins in urine. This condition results in  the overproduction of  abnormal immunoglobulins which are mostly? 
Select and explain. 
A. IgG, B. IgM, C. IgA, D. IgD
A: IgG
Answer: A: IgG 
Explanation: Multiple myeloma is due to the malignancy of a single clone of plasma cells in  the bone marrow. This results in the overproduction of  abnormal immunoglobulins, mostly (75%) IgG and in some cases (25%) IgA or IgM. In about 20% of the patients of multiple myeloma, Bence Jones proteins are excreted in urine which often damages the renal tubules.
Satyanarayana- Biochemistry, 3rd edition, pg-190