Which of the following lakes is the largest lake in africa, the world's second-largest freshwater lake, approximately 6,800 square miles large, and crossed by the equator?
a. lake tanganyika
b. lake chad
c. lake victoria
d. lake malawi

The World's second - largest freshwater lake is Lake Victoria, on the border between Uganda, Tanzania and Kenya. (the largest lake is lake Superior in Canada and United States - Its not in Africa, so Lake Victoria is the biggest lake in Africa.)
The equator also passes through it - so it's the correct answer!)