Barriers to trade in Ancient Rome (what made it hard to trade)

What did kublai khan learn from the chinese advisers he consulted?

Which of the following are details about the compromise of 1877? election results in a couple of states were in dispute and too close to call. samuel tilden would be given the win in exchange for the removal of federal troops. the presidential election was close between rutherford hayes and ulysses grant. it was agreed troops would leave the south in exchange for a hayes victory.

What was the most explosive issue facing the united states prior to the start of the civil war?