One factor that led to U. S. entry into World War I was the A.
sinking of the Leopard.
B.
sinking of the Lusitania.
C.
French use of submarine warfare.
D.
Japanese attack on Pearl Harbor.

If you help me I will help you

Explanation:

answer: secession

secession, as it applies to the outbreak of the american civil war, comprises the series of events that began on december 20, 1860, and extended through june 8 of the next year when eleven states in the lower and upper south severed their ties with the union. the first seven seceding states of the lower south set up a provisional government at montgomery, alabama. after hostilities began at fort sumter in charleston harbor on april 12, 1861, the border states of virginia, arkansas, tennessee, and north carolina joined the new government, which then moved its capital to richmond, virginia. the union was thus divided approximately on geographic lines. twenty-one northern and border states retained the style and title of the united states, while the eleven slave states adopted the nomenclature of the confederate states of america.

explanation:

i see, would you mind putting it as one?