What refers to any physical or tangible item that tends to prove or disprove a particular fact or issue?

Leukoderma is another name for ________, a disorder that causes large areas of decreased pigmentation to form on the skin

a. ringworm b. herpes zoster c. hives d. vitiligo

________ compounds are employed for thyroid studies, pyelograms, angiograms, and cholecystograms

a. Iodine b. Barium sulfate c. Iron d. Aluminum