Which of the following contributed greatly to the fall of the song dynasty?
a. the invention of gunpowder
b. the increase in the chinese population
c. the improvement of the civil service system
d. the vulnerability to invaders from the north

Why was "impressment" an important issue during the jefferson administration? the united states was being treated disrespectfully, as the spanish navy was forcing american sailors into naval service for them. the united states was being treated disrespectfully, as the french navy was forcing american sailors into naval service for them. the united states was treating british navy with disrespect by forcing british sailors into naval service for them. the united states was being treated with disrespect on the high seas, as the british navy was forcing american sailors off their ships and into naval service for them. the united states was treating french navy with disrespect by forcing french sailors into naval service for them.