In which country is Lake Onega located?

Which lake is the world's largest saltwater lake? What is the largest of the Great Lakes by volume? In which country is Lake Victoria located? In which country is Lake Issyk-Kul located? In which country is Lake Khövsgöl located? Which lake is the second-deepest lake in the world? In which country is Lake Poyang located? Which African lake is the source of the Nile River?