Before the Middle of the Fifteenth Century, Sub-Saharan Africa Had

Multiple Choice

Before the middle of the fifteenth century, sub-Saharan Africa had remained remote and mysterious to Europeans because  

A) there was little of value for them there.
B) sea travel down the African coast had been virtually impossible.
C) Islamic societies prevented Europe from making inroads there.
D) they did not know that it existed.
E) they feared the people who lived there.