. Inuits of the Bering Sea were in isolation from contact with Europeans longer than Aleuts or Inuits of the North Pacific and northern Alaska.
(A) in isolation from contact with Europeans longer than
(B) isolated from contact with Europeans longer than
(C) in isolation from contact with Europeans longer than were
(D) isolated from contact with Europeans longer than were
(E) in isolation and without contacts with Europeans longer than

Is OA C?

D???

this is (d).

* "isolated" is plainly better than "in isolation", so we can narrow the problem to (b) and (d) right away.
and if you entertained the thought of choosing (e) even for two seconds, you really need to read through a bunch of correct answers - just read through the correct answers - to get a handle for what the correct sort of english looks like on these things. "in isolation and without contacts" is not only laughably wordy, but also redundant (it says exactly the same thing twice).

before we look at the actual difference between (b) and (d), a general takeaway:
* if you have 2 ANSWER CHOICES THAT DIFFER ONLY IN THE PRESENCE/ABSENCE OF A LITTLE WORD, then CHANCES ARE THAT THE LITTLE WORD IS NECESSARY. i can't guarantee this 100%, but LOOK FOR AN AMBIGUITY that arises if the little word is omitted.
* if the little word isn't the _sole_ difference between 2 answer choices, then try to concentrate on the other differences between the answer choices first.

in this problem, (b) is ambiguous. it could mean one of the following 2 things: ("BI" = bering inuits, "E" = europeans, "A" = aleuts etc.)
* BI were isolated from E longer than BI were isolated from A
* BI were isolated from E longer than A were isolated from E
we can't tell.
if you add the "were", then the meaning is narrowed down to the latter of these two possibilities.

--

analogy:
i know more about shakespeare than my brother
ambiguous.
two ways we can resolve this problem by adding little words:
1) i know more about shakespeare than does my brother --> i'm a bigger shakespeare nerd than my brother is.
2) i know more about shakespeare than about my brother --> my brother and i were separated at birth, so i know more about shakespeare than i do about him.
same deal.