Why is the community so desperate to get jonas back?

Since Jonas is The Receiver and in the event that they don't have him then the history will be gone until the end of time. 
Jonas was chosen to acquire the position of Receiver of Memory, the individual who stores all the past recollections of the time before Sameness, as there might be times where one must draw upon the intelligence picked up from history to help the group's basic leadership.

3or 4 because it can’t be 1 or 2 because citizens who followed the renaissance were challenged the idea of religion and government

Ibelieve that the answer is (a).