How many decades are there in a century

a century is 100 years 100 is 10 squared so there is 10 decades. also a decade   is ten years

worldwide, 780 million people do not have access to an improved water source. an estimated 2.5 billion people lack access to improved sanitation (more than 35% of the world's population)

your answer would be a) no nation can be economically self-sufficient.

stay in school!