In my understanding:

In D, the stress is put on "five year"
And in E, the stress is put on "the highest price"

The highest price of gasoline is the thing that foreshadows little relief from the ongoing petroleum. So the focus should be on "the highest price"

Moreover, I think there should be a "dash" in option D: to a five-year high level

Correct me if I am wrong.

GMATMadeEasy wrote:Global market researchers have claimed that the recent increase in gasoline prices so that they were the highest price in five years foreshadows little relief from the ongoing petroleum

A>
B> -------
C> to what should be the highest price in five years
D> to a five year high level
E > to the highest price in five years

OA is E

Please explain difference in D and E .

Source Grockit

limestone has the right idea -- when you modify nouns with more nouns (instead of adjectives), it's common to hyphenate the expression to make it clear which nouns are acting as a modifier. I would expect five-year high level or (more correctly) five-year-high level, because "high" is being used as a noun, like an all-time high.

Jim@Grockit wrote:

GMATMadeEasy wrote:Global market researchers have claimed that the recent increase in gasoline prices so that they were the highest price in five years foreshadows little relief from the ongoing petroleum

A>
B> -------
C> to what should be the highest price in five years
D> to a five year high level
E > to the highest price in five years

OA is E

Please explain difference in D and E .

Source Grockit

limestone has the right idea -- when you modify nouns with more nouns (instead of adjectives), it's common to hyphenate the expression to make it clear which nouns are acting as a modifier. I would expect five-year high level or (more correctly) five-year-high level, because "high" is being used as a noun, like an all-time high.

But Jim , why is the OA E and not C ( because of redundancy , preciseness ? ).
I understand You have rejecetd D because of the misssing hyphen