A primary source is where the information comes directly from the original copy or someone who experienced it first hand, and where as a secondary source is someone or something that was not there when the event took place- hope this helps!!
The introduction is the beginning of an essay , when the readers read your essay the introduction is basically going to tell them the main idea or the plot , the introduction supports the whole thing that you are writing , basically you are giving all the things that are going to be discuss.Without this the whole body of the text is not going to be explicit as necessary .
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I think "excluded" would work well
I think it means that you should put in another idea
