Final answer:
The gluteus maximus muscle can contribute to back pain when weak, the sartorius allows leg crossing, and the gastrocnemius is the largest muscle in the lower leg.
Step-by-step explanation:
Weakness in the gluteus maximus muscle can lead to chronic back pain. The gluteus maximus is one of the primary muscles that stabilize the pelvis, and if it's weak, it can lead to improper alignment and pain. Additionally, when discussing which muscle produces movement that allows you to cross your legs, the correct answer is d. the sartorius. The sartorius muscle is the longest muscle in the human body and runs down the length of the thigh, allowing for crossing of the legs. Regarding the largest muscle in the lower leg, the answer is b. gastrocnemius. The gastrocnemius is a large and powerful muscle which helps in plantar flexing the foot at the ankle joint and flexing the leg at the knee joint.