Sentence Correction

Excavators at the Indus Valley site of Harappa in eastern Pakistan say the discovery of inscribed shards dating to circa 2800-2600 B.C. indicate their development of a Harappan writing system, the use of inscribed seals impressed into clay for marking ownership, and the standardization of weights for trade or taxation occurred many decades, if not centuries, earlier than was previously believed.

A.indicate their development of a Harappan writing system, the use of
B.indicate that the development of a Harappan writing system, using
C.indicates that their development of a Harappan writing system, using
D.indicates the development of a Harappan writing system, their use of
E.indicates that the development of a Harappan writing system, the use of

imo : e

my answ is E

the discovery*** indicates(!) that the development of a Harappan writing system, the use of

we need "indicates", because the noun of this verb is "the discovery".
we need "indicates THAT", since it is idiomatic.
and at last, we need "the use of" to make the phrase to be parallel to the word "the standardization of "

hope it helps

(E) is the clear winner. apart from what's been mentioned above, it also maintains parallelism...the use of inscribed seals.....and the standardization of weights

We dont know "their" refers to whom. So we can eliminate answer with "their" in it
A, C are eliminated
"indicate that" is proper grammar because we have "and" connects two noun phrase " the development of ..." and "standardization of..."
D is eliminate
Down to B and E
"discovery of...." is singular. B is clearly eliminated bc subject-verb agreement

Choose E make sentence parallel