HI there,

This is a common mistake. You must remember that there are certain error types that will ALWAYS be wrong (grammar errors and even certain stylistic errors/specific redundancies) but there are also error types that are considered as such most but not all of the time. Ambiguity is one such error type. If you have checked that everything else is wrong grammatically (or stylistically ie stylistic errors that are always wrong) and you are left with an answer choice that still has ambiguity, it can certainly still be right. Based on much research and analysis, we have seen this again and again.

In that particular question (which unfortunately you did not fully post here) D and E have wrong Idioms and must be eliminated. As for A and B the clarity of the sentence is compromised, which, on the whole, is of higher importance to eliminate than the ambiguous pronoun, which you perceive. More than this, in the clause after the semicolon, it is actually clear what 'it' refers to (the tool) because the whole modifier after the comma modifies this 'it'. So what seems to be ambiguous at first glance, is less so.