Final answer:
The hip flexors mentioned are the Rectus femoris and the Iliopsoas. The Rectus femoris aids in flexing the thigh at the hip as a part of the quadriceps femoris group, while the Iliopsoas is crucial for the same action, being a major flexor of the thigh.
Step-by-step explanation:
Among the options provided, C. Rectus femoris and D. Iliopsoas are both hip flexors. The rectus femoris, part of the quadriceps femoris group, is involved in flexing the thigh at the hip and extending the leg, while the iliopsoas, specifically the psoas major and iliacus forming the iliopsoas group, plays a major role in flexing the thigh at the hip. Other muscles listed, such as A. Bicep femoris (part of the hamstrings group), B. Gluteus maximus (which extends the femur), and E. Tibialis anterior are associated with other movements and are not hip flexors.