Question

History tells us how nations, once at the zenith of their glory.,__(suffered) decline

Answer 1

suffered is the rut answer.....

Answer 2

The phrase when completed would be written as:

History tells us how nations, once at the zenith of their glory suffered decline.

In the above sentence verb form used is simple past tense.

Simple past tense is used to depict an action that existed or happened before now. It is the basic form, action duration is not important as it can be in the distant past or recent past.

Certain time expressions are associated with a simple past tense that is:

Frequency - I sometimes ate those chips

A definite point in time- we went to the mall last week

An indefinite point in time- when I was a child, I loved playing hide and seek.