Final answer:
The correct choice for splinting when a female has been struck in the thigh with a large piece of equipment is to immobilize the leg with a splint to prevent further injury.
Step-by-step explanation:
A woman who has been struck in the thigh with a large piece of equipment and is experiencing swelling, deformity, and tenderness in the mid-shaft region should have her leg immobilized with a splint. This is the recommended course of action because it stabilizes the injury and prevents further damage. While administering pain medication and elevating the leg can be beneficial after immobilization, immediate immobilization is crucial to avoid further injury or disruption of any potential fracture.