<span>The third one i think is the right answer
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Please only add school related questions on here
A summary is a breif explanation/sum up of what you have talked about or what ever the topic was. It is used to wrap up everything you have explained. It is better to use summary's so that we can say the main idea in less words and so people can read it quicker and get the idea of that topic.
The SI base unit of length
