What discovery led to george b. mcclellan's victory over robert e. lee at antietam?

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What choice describe some of the difficulties john adams faced as president

Which effect did the united states supreme court's decision in plessy v. ferguson have? 1. ending segregation in all public schools in america 2. protecting voting rights for african americans by eliminating literacy tests 3. upholding the rights of all citizens to be treated equally by the government 4. authorizing the system that kept black and white people separated