Suppose That I Am a Professional Linguist with a Specialization

Multiple Choice

Suppose that I am a professional linguist with a specialization in African languages and I want to make the generalization that all African languages have an "S" sound.What would be the best way to go about looking for disconfirming instances?

A) Listen to languages spoken in Nigeria, where there are more languages than anywhere else in Africa.
B) Listen to six languages from north Africa and six languages from sub-Saharan Africa.
C) Listen to obscure languages that I've never studied from different parts of Africa.
D) Listen to the languages spoken in the four most populous countries of Africa.
E) Listen to the most well-known and documented languages of Africa.