Found in the wild only in Australia and New Guinea, powerful back legs

To tackle this type of question, you should begin by asking the fundamental question: who/what is the subject here.

In this case, who/what is found in the wild in Australia? Kangaroos!

Therefore, the subject Kangaroos should come immediately after the comma.

Once we have this down, we can eliminate Option A, B and C.

Now, we can turn our attention to Options D and E.

Option E uses ‘being’. Now, ‘being’ is not always patently wrong on the GMAT. So let’s look at this one:

Here, it’s a passive and awkward construction. The option also introduces ‘that are large’ which alters the intended meaning of the sentence.

Eliminate Option E.

Option D is the best choice.

Hope this helps!

Although I got to the correct answer because of POE, I would like to know how is the usage of "by" in the fragment " X are distinguished from Y by powerful legs with long feet" correct ?

As far as I know BY is used for following purposes;
1. BY introduces a means or method of particular action, or
2. After a passive verb, "By" introduces the agent of the action.

But i am a bit confused about the role of By in here.

Thanks

if we see a split between progressive tense and other tenses, we have to find out the reason to use progressive.

if the verb is action verb, progressive means that the action is happening at a point of time or in a period of time
when you come, I am eating my meal
if the verb is stative , such as to be, progressive means that the status is short.

"he is being good " means that "he is being good not permanently". it is possible that he normally a bad boy
so, if we use "kangaroos are being distinguished from" , we means the difference last a short time. this is not logical

Is the usage of "by" in option D correct ?
Further, why is option E incorrect ? Are we eliminating option E basis "being" or are there any other errors to eliminate the same?

GMATNinja bb Bunuel Skywalker18 AjiteshArun

Other mammals that are large makes it unnecessarily wordy. And in D there is no error IMO

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Yup, the "by" is fine in (D), since the "powerful legs with long feet" are what distinguish the kangaroos from other large mammals.

Here, we have a passive voice verb ("are distinguished"), and the "by" is used to indicate who or what is performing that action. This is a very typical construction -- for example, we could say something like "The platter of 20 burritos was eaten by the GMAT tutor" or "Tim was beaten up by Lou Ferrigno."

As for (E), "being" is indeed a problem because it makes it sound as though the process of being distinguished is ongoing. Does it mean that the kangaroos won't be distinguished from other large mammals until that process is complete? That doesn't make sense -- the kangaroos already have powerful legs with long feet, and that's what distinguishes them from other large mammals.

Also, "other large mammals by powerful legs" is simpler and easier to follow than "other mammals that are large by powerful legs". This unnecessarily wordy construction makes the "by powerful legs" modifier more confusing (at first glance it seems to go with the "that are large" part). It's not necessarily a dealbreaker, but it's another small vote in favor of (D).

I hope that helps!