This is the world's busiest airport in terms of the total number of passengers and total flights. it is the primary hub of delta air lines.

i really dont know the answer

this article will :

the right answer is the third one: turnpikes went short distances to connect markets. turnpikes, also known as toll roads, were very important for trade and transportation (of people, goods and products) in the 19th century, coinciding with the expansion towards the west. they contributed significantly to the economic development of the united states.