Mark the letter A, B, C or D on your answer sheet to indicate the sentence that best combines each pair of sentence in the following questions.

We arrived at the airport. We realized our passports were still at home.

A. It was until we arrived at the airport that we realized our passports were still at home.

B. We arrived at the airport and realized that our passports are still at home.

C. Not until had we arrived at the airport, we realized our passports were still at home.

D. Not until we arrived at the airport did we realize that our passports were still at home.