.The fact has worried many scientists ______ the earth is becoming warmer and warmer these years.
—We were not sure which way to go. In the end we chose to turn right. —You _______ the wrong way. You _______ left.
—Does Mr. Smith live next door to you? —No, but he _______.
______ for a long time, but he managed to catch up with his classmates at last.
I had just finished all my homework and was about to go to bed the phone rang.
--- How is Dennis getting along with his work? --- Well, he could always _______ a new idea for increasing sales.