Final answer:
To add participants to a video call on a mobile app, the host can usually use the 'Add Participant' button or send an email invitation; QR code options are less common, and all modern apps typically support adding participants.
Step-by-step explanation:
To add participants to a video visit via a mobile application, it usually depends on the specific app's features. The most common option is by using the Add Participant button within the app. This feature allows the host or the initiating member of the video call to include additional people directly from the interface of the call. Sometimes, an invitation can be sent via email by navigating to an option like Invite or Share Link, and requiring the participants to click the link in the email to join the call. However, not all video conferencing apps support the feature to add participants by scanning a QR code. The option that participants cannot be added via the mobile app is unlikely as most modern apps support this feature. It is essential to check the specific video conferencing application's help section or user guide for the exact methods supported.