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.
The buses began to pull out. Most of them were full of passengers.
A. The buses, most of which were full of passengers, began to pull out.
B. The buses, most of them were full of passengers, began to pull out.
C. The passengers, most of them were full of, began to pull out the buses.
D. The passengers, most of whom were full of the buses, began to pull out.
