Tens of Thousands of Sumerian Clay Tablets Have Survived

Tens of thousands of Sumerian clay tablets have survived,

A) but unfortunately the key to the language has not.
B) documenting the United Sumerian empire,which lasted from 2900 to 2500 b.c.e.
C) telling us more about Sumer than we know about any other human society at the time.
D) probably because the Sumerians kept them in special underground archives.
E) but all deal with priestly class and reveal nothing about Sumerian society.