While mother________ dinner, the phone rang.
A. Cooked
B. Had cooked
C. Has cooked
D. Was cooking
Chọn đáp án D
Alan took a photograph of Sandra while she________
D. Hadn’t looked
On July 20, 1969, Neil Armstrong ________ down onto the moon, the first person ever set foot on another planet.
In the last two decades, space exploration___great contributions to weather forecasting.
C. Made
The phone________ constantly since Jack won the first prize this morning.
If coastal erosion continues to take place at the present rate, in another fifty years this beach________ any more.