Which Statement Best Differentiates Indirect Noninvasive Vascular Test Procedures from Direct

Which statement best differentiates indirect noninvasive vascular test procedures from direct noninvasive vascular procedures?

A) Indirect test procedures provide morphologic information that allows evaluation of the severity of a lesion.
B) Indirect test procedures are physiologic and indicate the presence of significant occlusive disease by demonstrating pressure or limb volume changes downstream from the site of the lesion, whereas direct procedures evaluate the disease at the site where it is located
C) Indirect test procedures use continuous wave Doppler as well as plethysmographic testing.
D) Indirect test procedures detect lesions that are not yet hemodynamically significant, whereas direct test procedures give information only on disease that is flow reducing.