Who chose rulers of a system of heredity,(Aztec, Inca, Or Maya).

Why does less erosion & more deposition take place on the outside bank of a meander?

¿cual es mas alta en baja california, la migracion o la inmigracion?

Can someone me choose a broad topic and area of focus i am really doing this as a tally to see which one most people pick ok water pollution global warming endangered species atmosphere for the !