When is audio conferencing most successful?

a When participants are notified ahead of time

b When participants are in the same city

c When participants are vision impaired

d When participants are familiar with one another

A because your don't want to call anyone that is not available at that time

Audio conferencing is most successful when participants are vision impaired (C)

Explanation:

Audio conferencing is basically having a group of people coming together to share views or having deliberations or basically communicate with each other without actually seeing each other. and this is most effective if the parties are visually impaired. while audio-visual conferencing remains the best for people with correct vision