SC point

[botirvoy]

"Although the isolation of insulin was the most significant medical achievement of the 50ths, the real story behind it was not revealed for 50 years."

In the above sentence, can "it" create ambiguity? The intention is that it should refer to "the isolation of insulin".

thanks in advance!

[deshpande.harsha]

Remove "it" and read the sentence again. Having "behind" serves no purpose then. The "real story" should refer back to the action "insulation".

[esledge]

The "it" walks a fine line in your example. There are three singular nouns in the sentence:

(1) The subject in the although clause: "the isolation (of insulin)"
(2) The object in the although clause: "the (most significant medical) achievement"
(3) The subject in the main clause: "the (real) story"
Note: modifiers in parentheses.

Now, (3) can't be the antecedent of "it," so (3) causes no confusion. If the sentence meant to say "the real story behind the real story," then the reflexive pronoun would be required: "the real story behind itself..."

Between (1) and (2), the more likely antecedent is "the isolation," as subjects make stronger antecedent candidates than 'lesser' nouns. However, you could argue that either noun makes sense when inserted in place of "it":
(1) ...the real story behind the isolation of insulin...
(2) ....the real story behind the achievement....

I think the GMAT would probably be OK with this usage of "it." The subject status of "the isolation" gives us a good enough reason to consider it the antecedent. And even if we don't know whether (1) or (2) is the antecedent, the meaning is essentially the same: the isolation was the achievement...isolation = achievement.

Remove "it" and read the sentence again. Having "behind" serves no purpose then. The "real story" should refer back to the action "insulation".

I disagree that "behind" serves no purpose. This is a bit idiomatic: "the noun behind the noun."

Some examples:
The man behind the discovery...
The story behind the story...