Which of the following best completes the diagram above?

The correct answer is C “U.S. acquisitions in the late 19th Century”.  

Explanation:

In 1898, US and Spain signed the Treaty of Paris, a document in which Spain surrendered to US, giving the territories of Puerto Rico, Guam, and Philippines.

In the same year, U.S. Government annexed the island of Hawaii (after a coup d´etat that began in 1893, finally overthrowing the government of Queen Liliʻuokalani and annexing the territory five years later)

length of the cultivating season was not a problem of new england agriculture