I'm very confused with Pronoun Issue. In short I don't know when it ambiguously, or unambiguously refers to an antecedent.
For example

Innovations in the education industry have led to progressive reforms, and teachers have reorganized in response to recent legislation, forming a new union that helps them consolidate teaching techniques that they previously would have developed independently.

This is a question from Grockit, whose A is the answer.

The reason I thought this was wrong because the bold THEY.

"They" in this case can refer to Teaching Teachniques, Teachers, or even Refroms.

How can I clarify whether it's ambiguous or unambiguous.

Thanks[/b]