Please somebody explain what's wrong with D, it seems to me more appropriate. in S-V agreement and clearly refer back to 'posts'

The thirteen original British colonies in North America, some formed as commercial ventures, others as religious havens, each had a written charter that set forth its form of government and the rights of the colonists. A. some formed as commercial ventures, others as religious havens, each had a wri...

GMAT Prep says the OA is B, can someone please explain?

Hans Christian Andersen wrote fairy tales, which have been some of the most frequently translated works in literary history, while he wrote plays, novels, poems, and travel books, as well as several autobiographies, which remained almost unknown outside his native Denmark. (A) Hans Christian Anders...

I met the later version too, and it totally confused me.
For parallel, A should be the answer, as the OA
For modifier, D E should be the only choices, but they seems obvious wrong.
Maybe it's a mistake from GMAT itself.

the Oneida was the only one of the five-nation... I think the sentence takes the Oneida as 'one nation', should be a collective number, thus singular. However, A is flawed with other problem. 'the Oneida was the only one of the five-nation Iroquois League(s)' illogically means that 'Oneida' was one ...

in the original setence, 'vantage point...' serves as modifier, and E make the 'vantage point..' parallel to the main clause, is it a shift of the meaning?

Is A wrong for 'combining' ?