What Was an Important Early Drawback of the Clearboard System

Multiple Choice

What was an important early drawback of the Clearboard system by Ishii et al. (1993) .

A) it required people to move to a dedicated video conferencing facility at their workplace
B) as people moved closer to the board to talk with a remote colleague, the video system no longer picked them up
C) people found it uncomfortable to interact “looking down” at a colleague.
D) all of the above.