While cost savings and employee satisfaction have led many businesses

First, thank you for your PM and the tag, I appreciate you trying to understand the non-underlined portion of the sentence. And I hope you are doing so after zeroing on (D) as the right choice.

Second, I'd be lying if I said I am not afraid of "with phrases" myself. That's the only structure that still gets me baffled at times as it has had a fair share of ambiguity around its usage in GMAT questions.
So, I am not sure if I am the best person to write on the topic. Because there is no one litmus test for "with phrases" as there is for "Like/As" or "That/Which" structures. So, now I try to see how the "with phrase" sits in my sentence and whether it helps to convey the meaning of the sentence more clearly/precisely than the other choices available (this is the method suggested by legendary GMATNinja in one of his lecture videos on such tough-to-understand structures). But, I have tried to share my insight on "with phrase" structure as much as I can below, and I think AndrewN / sayantanc2k / AjiteshArun can provide better clarity on the topic of "with phrases" and their modification.

My understanding of "with phrases" is as follows:

Modifies preceding action:
With is a preposition. You use it to provide further information. For eg, I go to school with my sister. Main sentence here is. "I go to school", "with my sister", adds information on "with whom I go to school". So, "with" is a preposition. But when accompanied with a phrase, "with phrase" becomes a "Clause modifier". It tries to expound on the action with which it is used. Example: I drew a painting of my dead dog, with flowing strokes and teary eyes. Here, "with flowing strokes and teary eyes" is a "with phrase" describing how I drew the painting of my dead dog. I remember, I read a post by Magoosh's Mikemcgarry, sharing his insight on "with + verb-ing phrase" structure on an OG question. He wrote, "With phrases" do not add additional information/separate action. They just further detail the main action with which they are kept in the sentence. So, basically, "with +verb-ing phrases" are clause modifiers, which means, they modify the main action (verb) and make sense with the doer of that action (adverbial modifiers if you like the jargon).

Modifies preceding noun:
But, we know prepositional phrases can also modify nouns (adjectival modifiers, I think that's the jargon lol). When any modifier modifies a noun/pronoun, it does not expound on the action/verb (or how aspect of the action) associated with the noun/subject. Such as in the example, I drew a painting of my dead dog, with flowing strokes and teary eyes, with phrase expounded on the action of the previous clause and gave more information on "how" I drew the painting. But, when the prepositional phrase modifies a noun, it neither expounds on the action nor answers, "How was that action done?". Example: "Bihar is India's poorest state, with an annual per capita income of $111, lower than that of the most impoverished countries of the world" (link to this OG question is here). Here, the with phrase does not expound on "how" is Bihar India's poorest state. It infact modifies the preceding noun "India's poorest state = Bihar". To prove this, replacing "with" with "which has" gives, "India's poorest state, which has an annual per capita income of $111." Now, there is no doubt that "which" here modifies "the poorest state", which in turn modifies "Bihar". So, you can try this "with = which" trick and see if it makes sense with the noun. But, do not apply it blindly as people do in the case of "due to = caused by". It may/may not work always.

To take home the point, here is an excerpt from an egmat article that shows how "with phrases" can modify both preceding nouns and preceding clauses. Link to this OG question is here:
So, in my opinion, in the question at hand, the placement of "with phrase" is such that it modifies the noun "a communal office environment"."With phrase" here is modifying the preceding noun phrase "communal office environment" because the modifier presents description of a communal office environment. Also, the "its" in the with phrase needs to refer to some noun, only logical antecedent to its is a communal office environment in my opinion. Through the sentence, you get the meaning that "a communal office environment provides a centralized location for both collaboration and accountability", and this information is set off by a pair of commas as removing this information won't distort the actual meaning of the sentence that is, "Benefits of a communal office environment are enough to justify the costs of brick-and-mortar office space". So, "with phrase" here is also a non-essential modifier".

Hope it helps.

P.S: Please ignore any errors in the write up above. I returned from an excruciating field day and did my best to write a comprehensive article on "with phrase" modifiers to the best of my ability and I still know it's not the best you can get on that topic, so good luck fetching a response from the experts. But I have to say, in trying to help you, I too got my concepts cleared up a bit. And I think I am now less afraid of the "with phrases" than I was when I started to write this article, thus it proves the saying, "By helping others, you help yourself". So, thank you for thinking to ask.

OFFICIAL SOLUTION

This subject-verb agreement problem takes a different angle at testing that relationship between subject and verb. Whereas most agreement problems let you choose the verb to pair with a given noun, here you have to choose between subjects for a fixed verb. The key then is to find that verb, which is "are enough to justify..." about a dozen words past the underline. Since you're stuck with the plural verb "are" you must have a plural subject, "benefits."