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.
Answer:
The Cold War was important because it split the world into two rival sides that came into conflict with each other in a number of places around the world. This conflict has left us with, among other things, a huge aresenal of nuclear weapons, particularly in the US and in Russia.
The Americans hostility towards the clergy, adherents, and the Catholic Church during the 1800s was rooted to their desires to maintain the white, Protestant nation. The reform even led to religious discrimination and violence. Therefore, the answer to this question is most probably letter D.
Answer:
B-Darwin's "The Origin of Species"
