You _____ such a serious mistake if you had followed his advice.

After talking with his father for about half an hour, he felt better and began to know how to ________ this kind of situation.

We are flying at _____ altitude of 6,000 meters and perhaps we will get there at _____ midnight.

The party will start at 7: 00 sharpCome earlier— _____________

_________ useful invention the computer is.–Yes, It helps us a lot.