The transnational migration of people to a target country where they are not locals or residents in order to negotiate as inhabitants or green card holders is known as immigration.
The correct answer is Crop failures and revolutions in Europe.
The era of 1845, when the huge population was at the situation of movement from one state to another or were shifting from one nation to the other and were leaving their native or the resident place and were thinking to shift permanently at a place that can provide them their livelihood.
All the lands were left barren and no crops were cultivated. Europe was suffering was the revolutionary war and the people were saving their lives escaping from the war country to a peaceful country.
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