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 trade was encouraged with foreign states because they offered hospitality to foreign traders at Chinese ports. the invention of new medicines the establishment of a postal system there was development of commerce and communication in the region along the Silk Road

They  established of a postal system

The spread of weapons that used gunpowder

The extension of the grand canal in China  

The invention of new medicines

Explanation:

The Pax Mongolica refers to the stabilizing impacts of the conquests of the Mongol Empire on the social, cultural and economic life of the citizens of the vast Eurasian territory that the Mongols conquered in the 13th and 14th centuries.

the answer is trees if i'm not mistaken