Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions.
My sister didn’t leave the car key. As a result, 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.