Final answer:
The quadratus femoris is the muscle that inserts on the intertrochanteric crest of the femur. It functions as a lateral rotator of the thigh at the hip joint and aids in stabilizing the femoral head in the acetabulum. b) Quadratus femoris.
Step-by-step explanation:
The muscle that inserts on the intertrochanteric crest of the femur is the quadratus femoris. This muscle is one of the lateral rotators of the femur at the hip, which also includes the piriformis, obturator internus, obturator externus, superior gemellus, inferior gemellus, and the quadratus femoris itself.
The quadratus femoris is specifically responsible for laterally rotating the thigh at the hip joint and stabilizing the femoral head in the acetabulum.
The other muscles listed, such as the gemelli (both superior and inferior), obturator internus, and piriformis, have different insertion points.
The gemelli and the obturator internus insert into the greater trochanter of the femur, while the piriformis inserts into the top of the greater trochanter. Thus, the correct answer to the question of which muscle inserts on the intertrochanteric crest of the femur is b) Quadratus femoris.