Statement that serve as important national issues in the 1840s and 1850s is D. Immigration and slavery.
Around 1850s, the conflict as regards slavery can be regarded as a national issue which almost made United States to experience destruction.
And this always brings about unsettlement in the nation's political institutions as well as its public places.
Therefore, Immigration and slavery can be regarded as national issues around 1840s and 1850s.
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