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.

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Explanation:

the doctrine of nullification recommended that states living inside the union have the one-sided, inalienable ideal to void any law made by the national government that could be esteemed illegal.

the united states was shaped based on a general agreement among its individual states. hence, it is inferred that under the hypothesis of invalidation, since the states are the establishment of the union, they have the ability to referee and disprove unlawful laws.

a countries leader should be motivated by the common good of the country.