Final answer:
The joint that allows for opposition is the first carpometacarpal joint, formed between the trapezium carpal bone and the first metacarpal bone.
Step-by-step explanation:
The joint that allows for a unique movement called opposition is the first carpometacarpal joint.
Opposition is the thumb movement that brings the tip of the thumb in contact with the tip of a finger. This movement is produced at the first carpometacarpal joint, which is a saddle joint formed between the trapezium carpal bone and the first metacarpal bone. Thumb opposition is produced by a combination of flexion and abduction of the thumb at this joint.
Reposition refers to returning the thumb to its anatomical position next to the index finger.