Hi Stacey / Ron / MGMAT instructors,

I got the following SC question in my final CAT today:

During the twentieth century, the study of the large-scale structure of the universe evolved from the theoretical to the practical; the field of physical cosmology was made possible because of both Einstein's theory of relativity and the better ability to observe extremely distant astronomical objects.

because of both Einstein's theory of relativity and
by both Einstein's theory of relativity and
by Einstein's theory of relativity and also
because of Einstein's theory of relativity and also
as a result of both Einstein's theory of relativity and

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The OA is B and the OE states that there are two idioms to be recognized - "made possible by" and "both X and Y"

While I recognized the second idiom correctly during my attempt, the way I approached the "made possible by / because of" choice was as follows: in any passive voice construction, the portion after "by" should refer to the actual doer of the action and not to any circumstances or conditions that led to the action. Going by this logic, I thought that the portion "and the better ability to observe extremely distant astronomical objects" was actually referring to a condition / circumstance and not any doer of the action. Hence, I chose an option starting with "because of".

Should this rule not have been evaluated simply because "made possible by" is a "non-negotiable" idiom and therefore overpowers everything else?

As always, greatly appreciate your inputs.

Doesn't option B flout parallelism rules?

I understand that when we use the 'both' structure, the objects that are being talked about should have the same preposition or article before it.

for e.g.
This animal lives both in grass and in trees - parallel
This animal lives in both grass and trees - parallel
This animal lives in both grass and in trees - not parallel


Isnt the structure followed in option B the same as the last example here?
....by both Einstein's theory of relativity and the better ability to observe...

Correct me if I am wrong here.

The is not a preposition. The shared preposition is by.

Oops, missed the earlier question.

in any passive voice construction, the portion after "by" should refer to the actual doer of the action and not to any circumstances or conditions that led to the action

That would cause trouble here, if it were a reliable rule. Who says that it is?