Final answer:
In DeQuervain's disease, the extensor tunnel is developed in the 1) thumb.
Step-by-step explanation:
The extensor tunnel refers to the anatomical space in the hand where the tendons of the muscles responsible for extending the thumb pass through. These tendons run from the forearm to the thumb, passing through the carpal tunnel and being held in place by the flexor retinaculum.
DeQuervain's disease is characterized by inflammation of the tendons and their surrounding sheath within the extensor tunnel. This condition can cause pain, swelling, and difficulty in moving the thumb. Repetitive motion or overuse of the thumb and wrist can contribute to the development of DeQuervain's disease.
Therefore the extensor tunnel in DeQuervain's disease is developed in the thumb. This condition is characterized by inflammation of the tendons in the thumb, causing pain and difficulty in movement, the correct answer is 1) thumb.