Which were causes of the US entry into World war 1 ? select all that apply.

a. Germany threatened to invade the United the Unites States?
b. Germany refused to trade with the United States.
c. The Zimmermann Telegram angered US leaders.
d. The sinking of the Lusitania killed American civillians.

c and d

Explanation:

last two are ww2 so they wouldnt work

the law supported victims of political persecution.

explanation:

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).