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.

Peter heard a strange sound on the roof. He became very frightened.. 

A. On hearing a strange sound on the roof, Peter became very scared..

B. He became very frightened after he heard a strange sound on the roof.

C. He heard a strange sound on the roof and then becoming very terrified..

D. Peter became very frightened so he heard a strange sound on the roof.