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Help the time traveler finish his rather frantic incident report. Select ALL the grammatically correct phrases that can complete the sentence.
"____________ the keys to the time machine, the T-Rex wouldn't have eaten our packed lunches."
The correct answers are Had we not lost, If we had not lost, and If we hadn't lost.
This is a third conditional sentence describing an unreal past situation.
You can use the standard "if" clause (If we had not lost / If we hadn't lost).
You can also invert the subject and auxiliary verb to sound more formal (Had we not lost).
However, in inverted negative conditionals, the word "not" must follow the subject. Contracted negative inversions like "Hadn't we lost" are grammatically incorrect!