Final answer:
A) Economic opportunities and political instability. The Second Wave immigrants, including Mexicans, left their countries in search of economic opportunities and due to political instability.
Step-by-step explanation:
The Second Wave immigrants, particularly Mexicans, left their countries for economic opportunities and political instability (option A). Many of these immigrants were poor and sought a better life in the developed world. They migrated to the United States in search of low-paid labor jobs that offered them the chance to improve their way of life. These immigrants played a crucial role in the U.S. economy by taking on jobs that domestic workers were unwilling to do.