The Most Important Advantage of Northeast China That Mainly Contributed

The most important advantage of Northeast China that mainly contributed toward its being the industrial and technological center of the country in the 1970s and 1980s is:

A) its juxtaposition with China's most important industrial neighbors.
B) the lack of economic diversity in this area.
C) the existence of oil fields these areas.
D) that it contains Hong Kong, Macau, Guangzhou, and Shenzhen.
E) that it has the authority to impose embargoes upon its trading partners.