When boarding the plane, many passengers were annoyed because they ________ waiting in the airport for three and a half hours.
A. Are
B. Were
C. Have been
D. Had been
Chọn đáp án D
Alan took a photograph of Sandra while she________
D. Hadn’t looked
In the last two decades, space exploration___great contributions to weather forecasting.
C. Made
If coastal erosion continues to take place at the present rate, in another fifty years this beach________ any more.
The phone________ constantly since Jack won the first prize this morning.
On July 20, 1969, Neil Armstrong ________ down onto the moon, the first person ever set foot on another planet.