In the past, people ____ the world was flat.
thought
have thought
For many years the USA ____ a British colony.
was
has been
The USA ____ an independent country for over 200 years.
was
has been
Aborigines ____ in Australia for over 40,000 years.
lived
have lived
Dinosaurs ____ for 160,000,000 years.
have lived
lived
The earth ____ for more than 4,000,000,000 years
existed
has existed
Humans ___ on the planet for just 50,000 years.
were
have been