IMO :C

Quechua-speaking Ians seems idiomatic, like hindi speaking Indians, rather than Indians who speak hindi,

Tense : To describe event in past, simple past shared

Not choosing D based on meaning, it is not intended they shared th cuklture with but looks like shared culture of

Recently unearthed pottery fragments near the Atlantic coast of Brazil once belonged to early human inhabitants who shared much of the cultural customs of the Incas who were Quechua-speaking.

A] shared much of the cultural customs of the Incas who were Quechua-speaking
Customs can be counted.We need to use many

B] had been a people who shared many of the cultural customs of the Incas and were Quechua-speaking
Usage of past perfect is not justified.Further the sentence is wordy.

C] shared many of the cultural customs of the Quechua-speaking Incas
I am not sure..But I think shared ...of is unidiomatic

D] shared many culture customs with the Quechua-speaking Incas
Correct

E] were sharing much of the Quechua-speaking cultural customs of the Incas
improper usage of tense

What's the source?

I too picked D but OA is C.

Can anyone elaborate more on this ?

(D) is clearly better except for the word "culture." We are talking about "cultural customs" -- "culture customs" is unidiomatic and, frankly, I'm not even sure what it means!

(C), then, is the best choice left over. Its construction is similar to this:

"I shared many of my brother's toys," but with a longer possessive modifier, so it awkwardly becomes:
"I shared many of the toys of my brother."

Totally idiomatic, even though a bit long-winded. To Prachic, it's not "shared...of," it's simply "shared" and an object, with the "many of" construction being correct and idiomatic. The word "shared" does not have to be part of the "shared...with" idiom, although it can be.

Thanks Adam , i just missed the difference "culture customs" .... that was just like economic and economical .
Need to read very finely .