is there any way to tell if a teacher is currently 'on' and answering other question

No.

No. Recent answer-posting activity is all you have as an indication.

No, other than posting for one of us to tell. However, not everyone logs on to "show" themselves, so they could be on and we wouldn't know it.

Yes, there are a few ways to check if a teacher is currently available and answering other questions:

1. Check their online status: If you are communicating with the teacher through an online platform or messaging system, there is often an indication of whether they are online or active. Look for status indicators such as a green dot or "online" label next to their name.

2. Look for recent activity: If you are on a discussion board or online forum, you can review the timestamps of the teacher's most recent posts or responses. If they have been active within a short time period, it's likely that they are currently available and answering questions.

3. Directly ask the teacher: If you have a direct means of communication with the teacher, such as their email address or office hours, you can simply reach out and ask if they are currently available to answer questions.

Remember that teachers may have other responsibilities or commitments, so it's possible that they might not be immediately available to answer your question. Being patient and understanding is important when seeking assistance from an educator.