The answer is: Political bosses expanded their power by helping immigrants in return for their loyalty.
At that time, many of the political bosses realized that if they somehow can help the immigrants obtain their citizenship, the immigrants will become much more likely to return their favor.
This mean that they can influence the immigrants to vote for them during the election in exchange for the citizenship. This help the political bosses expanded their power.
The answer is A. Drove production costs up. It drove production costs down, because they were able to take less time to make the products as well as less materials because 1) standardized parts were invented around the same time, and 2) they didn't have people preparing everything so materials weren't wasted.
During the Abbasid dynasty, the city of Baghdad, located along the banks of the Tigris River, became a rich and cultured city as the new capital of the empire. The correct option among all the options that are given in the question is the second option or option "B". I hope that the answer helped you.