Answer:
The correct sentence is C. " Mass immigration into the United States began in the 1830s, when many Irish, Germans, and Scandinavians arrived. "
Explanation:
Sentence "A" incorrectly implies that the arrival ofIrish, German, and Scandinavian immigrants is merely an example andnot the main cause of the mass immigration of the 1830s;
sentence "B"
incorrectly implies that the arrival of Irish, German, and Scandinavianimmigrants was somehow contrary to the beginning of mass immigrationin the 1830s.