When did oxygen levels start to decline from 35 percent down to today’s levels

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

This document provides the framework for the united states government. it consists of three main parts: the preamble, seven articles, and 27 amendments.

What is one way that the congress of vienna changed the map of europe?