How did the mongol dynasty continue and expand the economic and political changes begun under the tang and song dynasties

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

Which choice describes some of the difficulties john adams faced as presiden

Which country was the last to join the allied powers? o great britain o france o united states o china