What motive was behind the push for more land like Hawaii
and the Philippines?

ask google there you might be able to find an answer for the question you're trying to ask

disease was the number one killer of native peoples. they had had little exposure to the diseases of europe. this led to some villages being almost completely wiped out and some tribes destroyed.

the united states broke it's neutrality was the constant german sinking of trading vessels resulting in the loss of lives, one example would be the lusitania.

either d or b, i'm not to sure. but my gut tells me it's prob going to be b