The correct answer to this open question is the following.
Although the question is incomplete because it does not provide a specific reference about the author of the letter or any other reference, we can comment on the following.
A primary source is the piece of information that was written by a character or an individual that lived in the moment of the event, was part of the event, or witnessed the event. This individual could have written a letter, or a document -including a book. Or he/she took a photograph. Or was part of an interview. The secondary source includes information from a third person who was not part of the time or event but has found information through other resources. It is the case of an encyclopedia or researchers/historian books.
Great Britain, France, The United States and The Soviet Union
The doctrine related to public education which was overturned by the Supreme Court decision in Brown v. Board of Education was the policy of B) separate but equal. This doctrine was overturned by referencing the equal protection clause of the Constitution which argued that equal protection of the law was afforded to all citizens regardless of race.
It would be "Polynesia" that was a region of Oceania greatly affected by European colonization, forced slavery, and deadly diseases, since this territory was highly advantageous for countries looking to increase production and expand their empires.
The correct answer is Moscow.
Each of the described can be found in Moscow, Russia.
