What is a reason that some historians provide to explain why many Americans support the idea that states’ rights caused the Civil War?

Many maintain that the primary cause of the war was the Southern states' desire to preserve the institution of slavery

Explanation:

- three-quarters or two-thirds..

- "the constitution provides that an amendment may be proposed either by the congress with a two-thirds majority vote in both the house of representatives and the senate or by a constitutional convention called for by two-thirds of the state legislatures."

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your answer would be (a)