The main purpose of this map is to illustrate the? 1.)sources of important natural resources
2.)development of United States imperialism
3.)growth of the Atlantic slave trade
4.)results of the Spanish-American War

(2) development of United States imperialism

Explanation:

the effect of the ming leaders banning ships with more than two masts was that there was no further construction of ships masts, because there was a surplus. ming emperors disallowed foreign exploration