Which of the following developments has caused recent controversy between richer and poorer members of the European union

The European Union's response to the migrant crisis has caused recent controversy between richer and poorer members of the European Union. As wealthier countries like Germany and France have taken in more refugees and migrants, poorer countries in Eastern and Central Europe have expressed resentment and resistance to accepting them. This has led to tension and disagreements within the EU about how to address the issue of migration and asylum.