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

A) that suggests that the elephant is descended from an aquatic animal, and its trunk originally evolved
B) that has suggested the elephant descended from an aquatic animal, its trunk originally evolving
C) suggesting that the elephant had descended from an aquatic animal with its trunk originally evolving
D) to suggest that the elephant has descended from an aquatic animal and its trunk originally evolved
E) to suggest that the elephant is descended from an aquatic animal and that its trunk originally evolved

I selected choice D, which turned out to be wrong. I guess I'm unclear why "is descended" is correct over "has descended". It seems as though the elephant was descended from the aquatic animal and continues to be so in the present. Perhaps it is simply an idiomatic thing.

The source of this question is the second GMAT Prep exam.

the two constructions have different meanings.
is descended --> used to talk about evolution, ancestry, etc. (as in this context)
has descended --> has moved, literally or figuratively, in a downward direction: the larynx has descended (literally) during the process of human evolution; our culture has descended (figuratively) into mindless entertainment

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there's also the issue of better parallelism in choice e: the repetition of the word 'that' creates more solid parallelism than that in the other choices.

Ron, I actually eliminated D & E because I thought "that" would follow more immediately after "found evidence" v. "to suggests". Is there a rule for when "that" is used? For example, sometimes I see it should be "however much that" or "she expressed anxiety that" and so I figure from practice I can learn the idioms but I'm are there any hard rules on this? Thank you!

can you please tell me what's wrong with C?

two things:
suggesting that the elephant had descended from an aquatic animal with its trunk originally evolving

blue part:
number one, it should be is descended, as per the discussion above (using any form of 'have' in this case suggests actual downward movement)
number two, much more importantly, the use of the past perfect is incorrect: the implication of the past perfect is that this isn't true anymore. (for instance, think about the statement 'i had thought he was an honest person'.)

orange part:
this modifier is not preceded by a comma, so it appears to modify 'aquatic animal': i.e., it mistakenly implies that the aquatic animal itself had the trunk that originally evolved blah blah blah.

unfortunately, the only hard and fast rule i can give you, in this case, is that you should pay attention to english idioms whenever you encounter them in your reading, conversations,** and so on - precisely because they are generally not governed by 'hard and fast' rules.

**restricted to relatively formal conversations with highly educated people, as all other conversations will most likely be laced with incorrect idioms. (the gmat has a way of tossing incorrect forms that are common in informal conversation into the wrong answer choices)