Incomplete question, here's the options that complete the questions:
A. external economies
B. the development of superior infrastructure
C. an abundant supply of skilled labor
D. New York City has one of the largest sea ports in the world
Answer:
A. external economies
Step-by-step explanation:
The summarizing reason for this unique advantage of New York City is the influence of external economies. The population is made up of a large number of foreign businesses which plays a role in New York's local economy and has placed it as the financial capital of the world.
This has thus given the city comparative advantage.