Final answer:
Grayscale imaging leverages pulsed wave ultrasound to determine the depth of tissue reflectors, constructing detailed internal body images using shades of gray.
Step-by-step explanation:
Grayscale imaging requires the use of pulsed wave ultrasound primarily to determine the depth of the reflector (option d). Pulsed wave ultrasound is a technique that sends short bursts of sound waves and then listens for echoes. These echoes return at different times depending on how deep the structures in the body are situated. The timing of the echoes allows the ultrasound machine to construct an image that represents the various depths of tissues, which appears as different shades of gray, hence the term grayscale. This ability to differentiate depth is essential in creating a detailed image of the internal structures of the body.