The pro-Union sentiment was strong in western Vir.ginia, eastern Tennessee, and western North Carolina because there were relatively few slaves or large plantations in these regions.
The pro-Union sentiment relates to the Union part during the American civil war.
The Unionism was very strong in the Vir.ginia's western counties which had close economic ties to Ohio and Pennsylvania.
Hence, the pro-Union sentiment was strong in these region because there were relatively few slaves or large plantations in these regions.
Therefore, the Option D is correct.
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