Answer:
A. European rulers agreed to respect one another's right to choose their kingdoms' religion
Explanation:
The Thirty Years' War was a war of religion that took place in the Holy Roman Empire, which comprises of four kingdoms, between 1618 to 1648, and concluded with the Peace of Westphalia in 1648
The Peace of Westphalia which officially introduced the model of peace being arrived at through a congress of diplomacy and new European political order that is founded on the principle of sovereignty of co-existing states and acceptance of the sovereignty of other states and a states right to decide its fate, principles of which are the founding bases of the present day international law
Therefore, a significant outcome of the Thirty Years' War is the agreement by European rulers to respect the right of one another to decide the religion of their kingdom
