Conditional meaning without explicit IF clauses - implied through context
Q1. I would have helped, but I ___ about the problem
Implied conditional: IF I HAD KNOWN. Ignorance is explained. Help was not given.
Q2. She would never have agreed, ___ the full circumstances
Inverted implied conditional. Knowledge was withheld. Agreement was obtained.
Q3. But for your assistance, I ___ failed
BUT FOR means IF IT HAD NOT BEEN FOR. Assistance was given. Failure was avoided.
Q4. ___ the weather, the event would have been perfect
HAD IT NOT BEEN FOR blames specific factors. Weather interfered. Perfection eluded.
Q5. What phrase introduces implied conditionals formally?
BUT FOR, HAD IT NOT BEEN FOR, and similar phrases imply conditions. Formality is maintained.