Question

when the biceps contract, the arm bends at the elbow joint. when the hamstrings contract—

the leg bends at the knee joint.

the leg bends at the hip joint.

the foot bends at the ankle joint.

Explanation:

The biceps are muscles related to arm movement at the elbow. Similarly, the hamstrings are muscles associated with leg movement. The hamstrings' main function is to bend the leg at the knee joint. Bending at the hip joint is mainly done by other muscle groups (like hip flexors), and bending the foot at the ankle is done by calf - related muscles (e.g., gastrocnemius for plantar - flexion).

Answer:

The leg bends at the knee joint.