How is it possible that an eyewitness account can be unverifiable?

The eyewitness is biased about the event.
The eyewitness is emotional about the event.
The eyewitness is the only person who saw the event.
The eyewitness shares multiple perspectives about the event.

The eyewitness is the only person who saw the event.

Explanation:

answer: what is the question?

explanation:

nothing certain is known about what happened, but it seems that the country declined gradually, perhaps due to bad government, or, more likely, due to a series of bad harvests, which resulted in widespread and recurrent famine.