Books are made __________ paper while paper is mainly made __________ wood.
The teacher asked the students _________________.
A low-carbon(低碳)lifestyle has an effectour daily life. More and more attention has been paid toenergies these days.
The teachers ________________ the office for a few minutes when we arrived.
——Would you mind my opening the window? ——__________.
—— He didn’t catch the train, did he? ——__________, though he was caught in the rain.