Answer: the second one, aan article from www.europeanhistory.net that was updated in 2008.
i’d say an article in the Journal of European History
This source isn't very recent (but it doesnt need to be because Amaya is writing about the history of Europe), but we do know that it was updated, which implies that more relevent information was posted. The information is coming from a trustworthy source (we know this because of the url the article is from), so is likely very relevent and relaible. The last source is irrelevent becasue it's abput a carmaker who had/has nothing to do with the Columbian Exchange, and the first source is from a journal (we don't know who the journal belongs to, or what kind of information is in it).
Geologists use the following tests to distinguish minerals and the rocks they make: hardness, color, streak, luster, cleavage and chemical reaction. A scratch test developed by a German mineralogist Friedrich Mohs in 1822 is used to determine mineral hardness.
