Answer:
D. its bitrate
Step-by-step explanation:
A. is incorrect, as "pixelated" refers to screen pixels (graphics)
B. is incorrect, as "megabytes" refers to file size. (Modern file compression can reduce file size while maintaining audio quality.)
C. is incorrect, as "frames per second" refers to video not audio
D. is correct, bitrate is often referred to in kilobits per second (for example, 320Kbps).