___ is well known is that Africa had contacts with India and the Red Sea civilizations from th

___       is well known is that Africa had contacts with India and the Red Sea civilizations from the earliest times．

A.As

B.It

C.What

D.That

答案及解析： C

解析：

考查名词性从句。此题考查的是主语从句，主语从句中缺少主语，所以用what，选C。