Final answer:
Doppler ultrasonography is the noninvasive technique used to evaluate blood flow in the body's main arteries and veins, such as those in the neck, arms, and legs.
Step-by-step explanation:
The noninvasive technique of evaluating blood flow through the major arteries and veins of the neck, arms, and legs is A. Doppler ultrasonography. This imaging technique harnesses the transmission of high-frequency sound waves into the body, which then generate an echo signal. This signal is subsequently converted into real-time images of anatomy and physiology by a computer. It is preferred in sensitive situations, such as during pregnancy, because it is the least invasive imaging technique. Doppler ultrasonography is particularly useful for assessing blood flow in the neck or extremities and can aid in diagnosing conditions like blood clots or blocked arteries.