Which term describes a time period marked by a change that begins a new period of development? century decade era millennium

An era describes a time period marked by a change that begins a new period.

An era :

Examples of eras include:

All the eras mentioned above were distinct in how people behaved so in conclusion we can say that an era is a time period that begins a new period of development.

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Era

Step-by-step explanation:

Century, Decade and Millennium have something in common and that which they have in common is that they are all measurement of time.

The keyword measurement implies that they are units of time just like seconds, minutes, hours, etc.

Century -> 100 years

Decade -> 10 years

Millennium -> 1000 years

However, era is used to describe events in history;

Take for instance; the era of the first generation of computer;

So, from the list of given options; Era best answers the question

answer: i don't understand. what are the options

step-by-step explanation: