Answer:
C. Format
Step-by-step explanation:
Bookmarks are for future reference, playback is for listening and scrolling through your project, and design, it's basically what it says, designing.
Formating is the size of the video, the frame, how and if it appears, and the actual timeline and video/audio/ogg file or mp3 itself.
from an after effects user.
and a semi music designer that uses audacity.
I hope this helps :)