Ineed a title for 'what do you think was the most important reason that the colonies decided to unite into a single nation? " this is canadian history btw

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.

the name of the theory is landmass theory.