**Core Concept:** Multiple myeloma is a plasma cell disorder characterized by the clonal proliferation of malignant B cells (plasma cells) within the bone marrow, leading to the production of monoclonal immunoglobulins (M-proteins) and bone lesions, renal dysfunction, and skeletal and extramedullary organ system complications.

**Why the Correct Answer is Right:** Multiple myeloma is diagnosed primarily using serum and urine electrophoresis to detect monoclonal proteins, also known as M-proteins. These are abnormal immunoglobulins produced by clonal plasma cells. The correct answer focuses on the laboratory tests used to detect M-proteins, which are the main diagnostic finding in multiple myeloma.

**Why Each Wrong Option is Incorrect:**

A. **False:** Bone marrow aspiration and biopsy are essential for confirming the diagnosis, but they are not the primary tool for diagnosis.

B. **False:** Imaging studies like X-rays, CT scans, and PET scans are important for evaluating bone lesions, but they are not the primary diagnostic methods.

C. **False:** Bone marrow examination is crucial for confirming the diagnosis, but it is not the main method for diagnosis, as mentioned above.

D. **False:** Genetic tests like FISH (fluorescence in situ hybridization) and cytogenetics are used for diagnosis, but they are not the primary methods for diagnosis in this context.

**Clinical Pearl / High-Yield Fact:** Multiple myeloma is associated with an increased risk of infections due to immunodeficiency, electrolyte imbalances, and renal failure. This highlights the importance of a comprehensive evaluation and early diagnosis to mitigate the potential complications and improve patient outcomes.

**Correct Answer:** D. **True:** Serum and urine electrophoresis, which detects the presence of monoclonal proteins (M-proteins) produced by the malignant plasma cells, is the primary diagnostic method for multiple myeloma.