mangipudi Wrote:I've rephrased the answer of an OG question below.
X will sometimes fail to detect Y when IT exists and will indicate that IT exists when IT does not.
1. In the sentence above does 'IT' unambiguously refer to Y or can it also also refer to X ?
All three occurances of IT unambiguously refer to Y. If the prepositional phrase "when..." were meant to modify the noun X, it would have to touch X. For example:
X, when it exists, will sometimes fail to detect Y...
When it exists, X will sometimes fail to detect Y...
The second occurance of IT is in the following structure: "X ...will indicate that IT exists..." If this IT were meant to refer to X, the sentence would read "X ....will indicate that itself exists..." (a bit awkward) or "X...will indicate that X exists..." (less awkward).
The third occurance is in a parallel structure with the first: "When IT exists...when IT does not." Therefore, same antecedent.
The link above addresses your second question (thanks selva.e). Let us know if you have follow-up questions!