Help LEGIT answers and braincells needed

Which is not a principal group in the Köppen system?

west coast climate

humid tropical climate

polar climate

dry climate​

Which of the following areas have the highest population density? a) quebecb) united statesc) californiad) new york city

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

What role did the waterways of europe play in development of europe's economy