Explain the causes of the civil war including the concept of states rights as well as why lincoln felt the constitutional need to keep the union intact

The Civil War is believed by most to be caused because of the issue of slavery. Some, however, believe that it was actually about states' rights, or the rights of states to govern themselves outside of the control of the federal government. ... Arguably the most significant of these was the issue of states' rights.

Explanation:

Attack Fort Sumter; this action began the Civil War. ... What role did the theory of states' rights play in the outbreak of the Civil War? The theory explained that the Constitution was a contract between independent states. The South felt the Union had broken the contract and had the right to secede.

offline recommendation systems option b

because recommendation systems produce a list of two ways

1. through collaborative filtering

or

2. through content-based filtering