Which is true of the middle colonies by the 1750s?
a. the middle colonies had developed strong economies and a stable culture based on the same heritage and background of the people.
b. philadelphia and new york city were both fairly small, but were beginning to develop a shipping trade that would later explode.
c. the middle colonies were the most diverse part of the thirteen colonies because of non-english immigrants.
d. several of the middle colonies were still struggling to build stable economies based on fishing and farming.

 The correct answer is : C.The Middle Colonies were the most diverse part of the thirteen colonies because of non-English immigrants.

Explanación :  Several immigrants arrived who left their countries of origin for religious freedom, to escape the war, find better opportunities in their economy and to be able to buy their own land. That freedom and acceptance, many people found them in the middle colonies. In the middle colonies lived many religious groups of different denominations. The cities in these colonies had more than one type of church unlike the New England colonies. For example, Philadelphia was founded with the aim that people from different backgrounds could live together in peace and harmony. With time it became the most prosperous city of the 13 colonies.

c it says nothing about connecting those 2 seas.