Australian embryologists have found evidence that
suggests that the elephant is descended from an
aquatic animal, and its trunk originally evolving as a
kind of snorkel.

=> Main structure that should be followed here is "that ABC and that XYZ".

(A) that suggests that the elephant is descended
from an aquatic animal, and its trunk originally
evolving

=> Originally evolving means it is still doing so, but the matter is not so.

(B) that has suggested the elephant descended
from an aquatic animal, its trunk originally
evolving

=> The suggestion is still okay, but using present perfect indicates that it is over. It should be present simple.

(C) suggesting that the elephant had descended
from an aquatic animal with its trunk originally
evolved
=> "Evidence suggesting" means it is still suggesting. On the other hand, the use of past perfect is not correct.
(D) to suggest that the elephant had descended
from an aquatic animal and its trunk originally
evolved

=> The issue is past perfect tense.

(E) to suggest that the elephant is descended from
an aquatic animal and that its trunk originally
evolved


The winner is E.

"is descended from" is an idiomatic expression and correctly used here.
"had descended" is wrong here coz we don't have any later past time marker that is generally needed in the case of Past Perfect.
A and B can be simply eliminated as they both use evolving .

Thus, E is the correct answer.

Thanks gmat_Tutor and sumanr,

"is descended" just doesn't sound right. But if it is idiomatic, there is nothing much to be done

On an other note ... what about "has descended"? Is there somthing I should be aware of while using that?

yep... I also held the opinion that "is descended from" does not seem right . But then I checked a couple of places and found that it is grammatically correct .
Wally is descended from Daniel Boone.

descend from someone or some group [for a living creature] - to come from a particular set of ancestors

debmalya_dutta wrote:yep... I also held the opinion that "is descended from" does not seem right . But then I checked a couple of places and found that it is grammatically correct .
Wally is descended from Daniel Boone.

descend from someone or some group [for a living creature] - to come from a particular set of ancestors

i agree...
the show spoiler was i think the OA given in question itself...
otherwise,i had serious doubt between D and E

past perfect...some action that had happended in past and completed...
in that sense,past perfect doenst seem to be evil here as both task is complete.