'Unlike' question

[dongkim2]

Unlike frogs that metamorphose from tadpoles into adults within a one-year period, it takes three to four years for the mountain yellow-legged frog of the Sierra Nevada to reach adulthood, and so they are restricted to deeper bodies of water that do not dry up in summer or freeze solid in winter.

o it takes three to four years for the mountain yellow-legged frog of the Sierra Nevada to reach adulthood, and so they are
o it takes the mountain yellow-legged frog of the Sierra Nevada three to four years until it reaches adulthood, and therefore it is
o in the Sierra Nevada, mountain yellow-legged tree frogs take three to four years to reach adulthood, thus being
o mountain yellow-legged frogs of the Sierra Nevada take three to four years until they reach adulthood, thus
o mountain yellow-legged frogs of the Sierra Nevada take three to four years to reach adulthood, and so they are

OA: E
[spoiler]
I was able to eliminate the choice A, B, and C because of the usage of unlike, but I chose D at the end. I also was not sure the meaning of the sentence after the last comma. Can anyone please explain? Thanks![/spoiler]

Source: GMATPrep

[prinit]

Unlike frogs that metamorphose from tadpoles into adults within a one-year period, it takes three to four years for the mountain yellow-legged frog of the Sierra Nevada to reach adulthood, and so they are restricted to deeper bodies of water that do not dry up in summer or freeze solid in winter.

o it takes three to four years for the mountain yellow-legged frog of the Sierra Nevada to reach adulthood, and so they are
o it takes the mountain yellow-legged frog of the Sierra Nevada three to four years until it reaches adulthood, and therefore it is
o in the Sierra Nevada, mountain yellow-legged tree frogs take three to four years to reach adulthood, thus being
o mountain yellow-legged frogs of the Sierra Nevada take three to four years until they reach adulthood, thus
o mountain yellow-legged frogs of the Sierra Nevada take three to four years to reach adulthood, and so they are

OA: E
[spoiler]
I was able to eliminate the choice A, B, and C because of the usage of unlike, but I chose D at the end. I also was not sure the meaning of the sentence after the last comma. Can anyone please explain? Thanks![/spoiler]




Source: GMATPrep

My pick is E. I also narrowed down my choices to D and E and then picked up E.
D mountain yellow-legged frogs of the Sierra Nevada take three to four years until they reach adulthood, thus -Unnecessary Until ..changing the whole context..
E mountain yellow-legged frogs of the Sierra Nevada take three to four years to reach adulthood, and so they are