OPTION A ; NOT CORRECT
This option did not elaborate on the subject matter as no sufficient information was established from any inference that would be drawn from it. Hence, it is not applicable here.

OPTION B; NOT CORRECT
This option contains the past participle elements "had been" which is in tandem with the tune of the writer as it inferred assertively that the action under consideration had taken place. It appears closer to grammatical correctness but definitely not the most suitable answer to this question.

OPTION C CORRECT ANSWER
This statement offers more skeletal support to the writer's position with more simplicity and contextual correctness without complex lexical structure. Also, the adjective "cultural" modifies the noun "customs".

OPTION D; NOT CORRECT
Here, two intangible nouns may not follow one another sequentially without the use of a separator like a comma (,) as in the case of "culture" and "customs". Hence, it is wrong.

OPTION E; NOT CORRECT
The write-up never suggested not does, it inferred it is a continuous action. It was something that has previously happened. The adjectival clause "were sharing much" doesn't conform with the original statement here.