Native peoples of America had no immunity to the diseases that European explorers and colonists brought with them. Diseases such as smallpox, influenza, measles, and even chicken pox proved deadly to American Indians. Europeans were used to these diseases, but Indian people had no resistance to them.
Yhe answer is the third one hope i could help
I hope this helps. they came, because of the widespread starvation in ireland in 1845. the california gold rush attracted chinese immigrants in 1849
