Is anyone here good at geography? (Map stuff)

What group has historically made up the largest portion of immigrants in mexico?

What is the "great pacific garbage patch"? (a) a large area of marine debris concentrated by rotating ocean currents (b) a large area around the pacific rim where debris collects from natural disasters such as tsunamis (c) an area in the pacific ocean where trash is intentionally dumped due to lack of landfill availability (d) a large trash dump located in hawaii

In a scientific experiment, a is any factor that can be changed or be changed