Final answer:
William Lloyd Garrison correctly predicted the eventual separation between free and slave states, which was in line with the tensions leading to the Civil War and reflected in Lincoln's 'house divided' speech.
Step-by-step explanation:
The student has asked which events William Lloyd Garrison correctly predicted would be unavoidable. Garrison, a prominent abolitionist and publisher of The Liberator, played a vital role in portraying slavery as a national sin and called for its immediate end.
Out of the options provided by the student, Garrison did not foresee the unity of the United States as slave states only nor the end of the Bible being used to attempt to justify slavery. He also did not predict the decline of militant reformers known as "free-soilers" or the end of cotton's hold on the economy due to drought. What he correctly predicted was the eventual separation between free and slave states. This foresight aligned with the tensions that led to the Civil War and was echoed by leaders like Abraham Lincoln, who spoke of the 'house divided' metaphor. Lincoln anticipated that the United States would not endure permanently as a nation half slave and half free, suggesting an inevitable division on the issue of slavery.