You can best infer that the battle of shangai was fought

answer: the ocean

explanation: if you map out 30 n and 40 n latitude, you will get the ocean

answer; andrew jackson approved nullification by signing it into law,and john calhoun opposed it saying it was unconstitutional;

four sitting presidents have been assassinated while in office but the first was abraham lincoln,

the anwser is a) to prevent military conflict