usage of which in case "X of Y"

[parveenjain]

executives-sc-from-og-usage-of-which-t1651.html
Hi Ron,
I saw your post about the rule of "which" for X of Y.I followed this instruction on another question given here:
Under most conditions, an atom of one of the noble gases is inert because their outer orbital contains the maximum number of electrons; the completion of their outer orbital makes these elements more stable and less able to react with other atoms and molecules.
A) because their outer orbital contains the maximum number of electrons; the completion of their outer orbital makes these elements more stable and less able to react with other atoms and molecules.
B) because its outer orbital contains the maximum number of electrons; the completion of the outer orbital makes the atoms of the elements more stable and less able to react with other atoms and molecules.
C) because its outer orbital contains the maximum number of electrons, which makes these elements more stable and less able to react with other atoms and molecules.
D) because their outer orbital contains the maximum number of electrons, making these elements more stable and less able to react with other atoms and molecules.
E) because their outer orbital contains the maximum number of electrons, and the completion of their outer orbitals makes these elements more stable and less able to react with other atoms and molecules.
source - http://www.platinumgmat.com/practice_gm ... ion_id=181
this question is assailable to everyone.

Here the OA is B.I opted for C because I felt the usage of "which' here is right(because of 'X of Y' usage).
Can you please help me to explain for this.

Thanks.

[kbhardwaj]

Here is my understanding.

According to "X of Y", which is referring to "the maximum number of electrons".

But what is making the elements more stable? Is it the maximum number of electrons? Or is it the outer orbital containing the maximum number of electrons? The answer is: the outer orbital containing the maximum number of electrons.

Therefore in the correct sentence, we either need a modifies which modifies the complete clause "its outer orbital contains the maximum number of electrons" or have a new independent sentence as is the case with option B.

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Kb