Which is the BEST reason why the United States sent ships led by Commodore Perry to Japan in 1868?

A. The United States wanted to gain Japan as an ally against China after the Boxer rebellion.

B. The United States had the intention of imperializing Japan in order to expand its' borders.

C. The United States wanted to import more laborers from Japan, in order to expand their growing industrialism.

D. The United States desired to open up trade with Japan, which previously had been mainly closed to trade with foreigners.