This is a personal question, which means that only you can answer it. However, I can give some examples that might help guide your work.
An example of a primary source that you might encounter in your own life is that of a news article. As this article is likely to be written by a reporter witnessing the events, it can be considered a primary source. On the other hand, an example of a secondary source would be a non-fiction book that talks about a historical event. This is because such a book would give a second-hand account of an event based on historical information.
The louisiana purchase in 1803 doubled the size of america
Answer:
Is there any more to the problem?
Well we know that it is not A or C, Reason: Some states have up to 5m people in it. (For example about 8 live in just new York alone.)
And we also know its not 10 billion. Reason for this: Scientist have proven that there is no more then 8 billion people today.
And so now we got 6.5 billion is the closest, the real number is about 7.5 billion.
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