Black opaque or cardboard film mounts are preferred because they

A) are less expensive and more readily available from the manufacturer.
B) are more common and therefore easily shared with other practices.
C) make placing films in the windows easier.
D) block extraneous light to aid in interpretation.

D
Explanation: A) Black plastic or gray cardboard mounts are often preferred over clear plastic mounts because they can block out extraneous light from the viewbox, enhancing viewing and interpretation.
B) Black plastic or gray cardboard mounts are often preferred over clear plastic mounts because they can block out extraneous light from the viewbox, enhancing viewing and interpretation.
C) Black plastic or gray cardboard mounts are often preferred over clear plastic mounts because they can block out extraneous light from the viewbox, enhancing viewing and interpretation.
D) Black plastic or gray cardboard mounts are often preferred over clear plastic mounts because they can block out extraneous light from the viewbox, enhancing viewing and interpretation.