Why do astronomers think that there may be other advanced civilizations?

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

Which of the following types of tourist are best to bring money to the local southeast asian communities

The separation of northern ireland from the republic of ireland is an example of