What is the purpose of a poster frame?

a) to allow the contents of an embed code to be displayed
b) to insert a downloaded video for offline playback and editing
c) to create the frame in which a screen recording will be inserted
d) to capture a portion of a video clip to show as a preview image

D) to capture a portion of a video clip to show as a preview image

since it can be assumed that what aslam is making is a template by compiling all the commonly used excel formatting in several worksheets in an excel document, aslam can choose to save it using the .xltx or .xltm format instead. thus, aslam can distribute the templates he has made to his team members in an easier manner.

plot immersion i am not fully sure with it though