Southern states passed laws after 1800 to discourage manumission because southern whites feared that freed blacks would seek revenge for past treatment as slaves.
Manumission takes place when masters free their slaves voluntarily. This government abolished slavery from it's roots completely. It is a formal process by which a slave owner can give his slaves their legal freedom. During the period of American slavery from the 1600 to 1865, it was one of the main avenues available for a slave to obtain his or her freedom.
Therefore, last option is the correct answer.
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