Option C. Gun powder is the major invention during the Mongolian invasion of Jin and song dynasty. Hand grenades were used with the help of gunpowder. It used to be the most destructive land warfare strategy. Mongolians used hand canons with which they hurled the gunpowder balls.
Caltrop is a hollow pottery which is filled with gunpowder and iron pieces. When the caltrops explode, the sharp edged iron piece would get stuck in the body of the opponent which causes immediate death.
Genghis khan is the first to establish Mongolian Empire and was known for his brutal military operations.
