Insertion of iliocostalis lumborum?

• A. Angles of the lower ribs and transverse processes of the lumbar vertebrae
• B. Spinous processes of the upper thoracic vertebrae
• C. Mastoid process
• D. Greater trochanter

Answer: (A)

The key idea here is where the iliocostalis lumborum attaches (its insertion). This part of the erector spinae runs from the pelvis and lower spine upward to the ribs, and for the lumborum portion the distal attachment is at the angles of the lower ribs and the transverse processes of the lumbar vertebrae. That specific attachment pattern lets the muscle extend the spine and laterally flex it when acting on one side.

So the correct insertion matches exactly: onto the angles of the lower ribs and the transverse processes of the lumbar vertebrae. The other choices don’t fit the muscle’s typical distal attachments—spinous processes of the upper thoracic vertebrae would point to a different muscle or region, the mastoid process is for neck/head muscles, and the greater trochanter is the hip region.