How did immigration to the United States from Europe change between 1840 and 1850?

It more than tripled.

Explanation:

Between 1840 and 1850, immigration from Europe to the United States more than tripled, getting to a total immigrant population of 1,713,000, including over 781,000 Irish, 435,000 Germans, 267,000 British, and 77,000 French people. The Irish, German, and Scandinavian immigrants entering during the 1840s and 1850s were part of the second wave of European immigration, that was escaping famine, religious oppression, and political conflicts.

nothing certain is known about what happened, but it seems that the country declined gradually, perhaps due to bad government, or, more likely, due to a series of bad harvests, which resulted in widespread and recurrent famine.

d. it spread christianity. i just took the test and got it right.