Which of the following muscles attaches to the femur and calcaneus?

The gastrocnemius is the correct choice because it is a major calf muscle that originates from the femur and attaches to the calcaneus via the Achilles tendon. This muscle plays a crucial role in movement, particularly in activities such as running, jumping, and walking, where it is responsible for plantarflexion of the ankle and flexion of the knee. By connecting the femur to the calcaneus, the gastrocnemius effectively facilitates the integration of movements in the lower leg, making it essential for various types of locomotion.

The other muscles listed do not connect both the femur and calcaneus. The rectus femoris primarily works on the hip and knee, the tibialis anterior is involved in dorsiflexion of the ankle and originates from the tibia, and both the rectus femoris and tibialis anterior do not have attachments on the calcaneus. The soleus muscle does attach to the calcaneus but originates from the tibia and fibula, not the femur, making it distinct in its point of origin compared to gastrocnemius.