The term 'aspect ratio' is a specification of ... A. software.
B.
paper size.
C. printers.
D. monitors.
(1)

I believe the correct aswer is D. Monitors

Explanation:

The aspect ratio of a display device is the proportional relationship between the width and the height of the display. It is expressed as two numbers separated by a colon (x:y), where x corresponds to the width and y to the height. Common aspect ratios for displays, past and present, include 5:4, 4:3, 16:10 and 16:9.

I hope that help!