My sister didn’t leave the car key, so I couldn’t pick her up at the airport.
A.If my sister left the car key, I would pick her up at the airport.
B.If my sister had left the car key, I would have picked her up at the airport.
C.If my sister have left the car key, I would have picked her up at the airport.
D.If my sister had left the car key, I could pick her up at the airport.