Final answer:
Others can participate in the video visit by joining as audio participants using their phones.
Step-by-step explanation:
The correct answer is b) They can join as audio participants using their phones. When the maximum limit of 7 people participating in the video visit has been reached, others can still participate by joining as audio participants using their phones. Even though they won't be able to participate visually, they can still join the conversation and interact with the other participants through audio.