The correct statements about Songhai are:
- Songhai leader Sunni Ali conquered Mali and destroyed the city of Timbuktu. (This statement is correct.)
- During the reign of Askia Muhammad, the Songhai empire reached its greatest size. (This statement is correct.)
The other two statements regarding Mansa Musa and Leo Africanus are incorrect in the context of Songhai:
- Mansa Musa was a ruler of the Mali Empire, not Songhai.
- Leo Africanus was not Songhai’s ambassador but is often noted for his writings about the region during the time of the Songhai Empire, but he was not an ambassador for them.
So, the two correct responses are the first and the last statements.