Final answer:
The Radial artery, which is formed at the bifurcation of the Brachial artery and supplies blood to the lower arm and carpal region, is the correct secondary injection point used to clear the thumb and index finger.
Step-by-step explanation:
The artery could be used as a secondary injection point to clear the thumb and index finger. The correct answer is b. the Radial artery.
The Radial artery is formed at the bifurcation of the Brachial artery, running parallel to the radius bone. It branches off to supply blood to the lower arm and carpal region. Upon reaching the carpal area, it fuses with the ulnar artery to form both superficial and deep palmar arches that deliver blood to the hand, including the thumb and index finger. Therefore, the radial artery is the appropriate site for a secondary injection aimed at affecting these areas.
It is important to note that none of the other options listed (Carotid, Brachial, Femoral arteries) serve the specified function for the thumb and index finger areas, as they are responsible for supplying blood to other body regions.