Which innovation promoted trade and contributed to the unity of the persian empire?

Use of standardized metal coins.

Explanation:

According to a different source, these are the options that are included with this question:

The use of standardized metal coins was the main innovation that allowed the Persian Empire to become more unified. As many people shared such coins, they began to see themselves as members of the same society. Moreover, these coins allowed trade to expand and become more efficient.

abraham lincoln, according to anyone who was connected with agriculture, represented the worst of northern politicians. shortly after lincoln was elected, south carolina seceded from the union. they along with other southern states, retained their anger. in a way, it was their own fault: the democrats were split in the south. some wanted slavery to be extended in other states that were about to join the union and some didn't want it badly enough. lincoln had a solid backing from his party: the republicans were united in not wanting slavery to be expanded.