Help please history Knights During Feudal Times

Ateam of scientists studied the sediment at the bottom of an ancient lake. they were able to determine the weather conditions of the indus valley in ancient times. they found that the entire area had suffered a drought after the monsoons declined. this drought lasted 200 years. because of the drought, there wasn’t enough food or water. the people of the indus valley were forced to leave their cities.

Which four of these developments were made under mongol rule during the pax mongolica? the extension of the grand canal in china the spread of christianity the spread of weapons that used gun powder the invention of new medicines the establishment of a postal system the invention of geometric models of lunar motion

Ineed the answer ! what year was the 13th amendment passed in the us?