Which of the Following Factors Has Limited the Information Available

Which of the following factors has limited the information available to scholars studying the Harappan society?

A) Building materials were made of sandstone, which did not withstand the wear of time.
B) Most sites indicate that they were destroyed in invasions, leaving little to study.
C) Harappan script has not been deciphered.
D) Present-day national turmoil has limited diggings.
E) Ancient Indian towns had little contact with each other, and scholarly comparisons have been limited.