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.
For fear of waking up the family, Trung tiptoed upstairs.
A. Trung tiptoed upstairs because he didn’t want to wake up the family.
B. Trung tiptoed upstairs so as not to wake up the family.
C. The family feared when Trung tiptoed upstairs.
D. Trung tiptoed upstairs lest the family should be woken up.