恐龙时代是地球历史上的一个重要纪元。

The age of dinosaurs was a remarkable ___epoch in Earth's history.

恐龙灭绝发生在白垩纪的最后一个时期。

The extinction of dinosaurs occurred in the last ___epoch of the Cretaceous period.

蒸汽机的发明标志着一个工业新纪元的开始。

The invention of the steam engine marked the beginning of a new ___epoch in industry.