Why are the three river systems (Indus, Ganges, Brahmaputra) a key to life in South Asia?

They carry fertile soil to floodplains allowing agriculture
They provide water for the mountains
They the major food system for South Asia

In 1933 the 21st amendment was added to the u.s. constitution, allowing for the manfacture, transportation, and sale of alacoholic beverages in the united states. why was this amendment needed?

If we represent the solar system on a scale that allows us to walk from the sun to pluto in a few minutes, then a) the planets are microscopic and the stars are millions of miles away. b) the planets are the size of basketballs and the nearest stars are a few miles away. c) the planets are marble size or smaller and the nearest stars are thousands of miles away.

Why isn't the balkan region good for farming? it has dry summers. it is far from the sea. its soil is not fertile. its terrain is mountainous. its winters are mild.