By ________ time we had just left the office, ________ alarm went off. A. Ø / the B. a / an C. a / the D. the / an
By ________ time we had just left the office, ________ alarm went off.
A. Ø / the
B. a / an
C. a / the
D. the / an
By ________ time we had just left the office, ________ alarm went off.
Chọn đáp án D