Final answer:
Arthroscopy (A) is the diagnostic test used for direct visualization of joints' internal structures, such as ligaments and menisci, which involves inserting an arthroscope through a small incision.
Step-by-step explanation:
The correct answer to the question is A) Arthroscopy. This is the diagnostic test used for the direct visualization of ligaments, menisci, and articular surfaces of joints. Arthroscopy involves a small incision through which an arthroscope, a pencil-thin instrument, is inserted to view the joint interior. This procedure allows a surgeon to observe and treat issues within the joint such as torn menisci or ligaments.
Arthrography is a medical imaging technique but it uses a contrast agent and X-rays to visualize the structures which is different from the physical inspection that arthroscopy provides. Unlike the other options provided such as muscle biopsy, ultrasonography, or electromyography, arthroscopy is a surgical technique that directly visualizes and treats the internal structures of a joint.