Sentence Correction

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.

(A) that suggests that the elephant is descended from an aquatic animal, and its trunk originally evolving
(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 evolved
(D) to suggest that the elephant had 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 have a few questions:

What is "is descended" construction, has descended present participle.

Secondly for A the OG says that sentence after and is not parallel. The and there is after a comma, making it an independent clause which per my understanding doesn't need to be parallel, it lacks a verb so making it a run on sentence (evolving is not a verb because it is not preceeded with a to be verb).

In Choice C the OG says with cannot be followed by an independent clause, what does it mean by that.

Lastly the OA is E, which has a to suggest an infinitive. What is the rule for using infinitives?

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.

(A) that suggests that the elephant is descended from an aquatic animal, and its trunk originally evolving - Evolving is incorrect, correct usage should be evolved so so A is out
(B) that has suggested the elephant descended from an aquatic animal, its trunk originally evolving - same as A
(C) suggesting that the elephant had descended from an aquatic animal with its trunk originally evolved - Evidence is not suggesting, Australian Embryologists are, therefore out
(D) to suggest that the elephant had descended from an aquatic animal and its trunk originally evolved - To suggest X and Y .. X and Y should be parallel.. i.e... that the elephant.. and that its ...(here the second that is missing)
(E) to suggest that the elephant is descended from an aquatic animal and that its trunk originally evolved - Maintains parallelism.

I have a few questions:


Lastly the OA is E, which has a to suggest an infinitive. What is the rule for using infinitives?

If you browse around on other forums you'll reach a conclusion that there is no specific rules as to when infinitives should be used. The main deciding factors is structure and parallelism.

Also.. remember that , -ing construction modifies the entire preceding clause, so you can always check whether using -ing form just after the comma makes sense...

Please ensure that you double check with some experts before you follow what i have suggested.