Answer:
B. era
Step-by-step explanation:
The word epoch means: a period of time in history.
We want to find a synonym for epoch, or a word that has the same meaning. So, if we were to replace epoch, the sentence would be the same.
Calendar: a chart showing the days, weeks and months of a year
Era: period of history that is long and distinct
Millennium: period of 1000 years
Timeline: a graphic representation of time passing
The word that makes the most sense as a synonym for epoch is era.
Therefore, the correct answer is B: era.