Question

One reason for the mass migration of many Irish

to North America in the 19th century was
(1) a series of crop failures
(2) enforcement of a military draft
(3) civil war in Ireland
(4) an outbreak of malaria

Answer 1

1. A series of crop failures.

Answer 2

One reason for the mass migration of many Irishto North America in the 19th century was a series of crop failures
This is what sent them to North America in the 19th century.