Hey There!!
Your best answer choice will be is Were.
Because You were the most important person at the time makes sense. But, If you put You was the important person at the time doesn't make sense at all... Hope This Helps!!
By ♡~Itsbrazts♡~
Supposed*
You had a grammatical error and I had to fix it considering you’re an English teacher.
Answer:. The authors states that in-person classes are better than online classes.
Explanation: