The resumption of unrestricted submarine warfare by Germany, from 31 January 1917.
<span>German u-boats were sinking US merchant ships and killing US seamen even though USA was a neutral. Further, ships of other neutral nations sailing to and from the US were also being sunk.All this was adversely effecting the US economy.
Hope this helps :)</span>
The answer is D. Vietnam successfully resisted Chinese attempts at occupation, while japan was never engaged in direct conflict with china.
Presidential appointments must be confirmed by the United States Senate
The arrival of the U.S. troops in Europe. (I just learned about this in school)
