What system................
They could not ban slavery in slavery in any of the slave states. After this ruling, slave states have celebrated and labeled the constitution as a pro-slavery document. This also angered abolitionists who wanted to ban slavery
The right answer is the third one: the bubonic plague originated in the Gobi Desert, part of the then Mongol Empire, around 1320. It then propagated to China and subsequently to India, Europe and Russia. The disease spread via trade routes mainly as a result of a poor hygiene. It never reached the American continent or Sub-Saharan Africa.
Answer: The incorporation of Eastern Asian ideas and knowledge into mainstream European society
The European practice of religious tolerance based on the example of the Mongol Empire
A political alliance that protected Western Europe from further invasions of the Mongol Empire
An increased European awareness of important cultural, political, and economic developments in Eastern Asia
Refer to the passage.
"The next day (25th May) (the Chan) sent his secretaries to me, who said: ‘Our lord sends us to you to say that you are here Christians, Saracens [Muslims] and Tuins. And each of you says that his doctrine is the best, and his writings—that is, books—the truest. So he wishes that you shall all meet together, and make a comparison, each one writing down his precepts, so that he himself may be able to know the truth.’ Then I said: ‘Blessed be God, who put this in the Chan’s heart. But our Scriptures tell us, the servant of God should not dispute, but should show mildness to all; so I am ready, without disputation or contention, to give reason for the faith and hope of the Christians, to the best of my ability.’ They wrote down my words, and carried them back to him. Then it was told the Nestorians that they should look to themselves, and write down what they wished to say, and likewise to the Saracens [Muslims], and in the same way to the Tuins.”
Excerpt from The Journey of William of Rubruck, written by a Franciscan monk sent by King Louis IX of France to the Mongol Empire in 1253
There are many reasons as to why trench warfare was so costly in humans. One reason was because men were ussually in the same place and as a result, the enemy knew where to strike. For example, the enemy would know the exact location of a group of people. The enemy calculates the possition and fires a mortar at that direction, killing a bunch of people. There are many other scenarios like this one... aircrafts, bombs, ect.