What did imperial nations have to do to protect their economic interests?

a. they imposed high taxes on foreign products.
b. they exported products to foreign countries.
c. they built large armies,
d. they built large navies.

Imperial  nations built a strong navy and military to protect their economic and political interests.

Explanation

United states is the maritime strategic country wherein it has chosen to rise and build a strong navy in order to express the globe, it superiority and also to promote the economic interests of the country. It is also to be observed that a strong naval base served to be an added advantage during the wartime too. United states was having good trade relations with the European countries and its allies.

Naval appropriation bill was also passed in congress which insisted the federal government to allocate funds for the purpose developing the US naval operations.

i really really really really really really dont know

oil! is what i am assuming