HE WAS WRITING TO HIS FRIEND WHEN HE ... A NOISE.A. WAS HEARINGB....

42. - 3500 CAU TRAC NGHIEM ON TAP AV THCS
3500 CAU TRAC NGHIEM ON TAP AV THCS

42. He was writing to his friend when he ... a noise.

a. was hearing

b. heard

c. had heard

d. hears

 b