People throughout the world together now to protect the natural environment.
A. are working B. worked
C. will work D. have worked
A： have you talked with your friends on Wechat？
B：Since I came back from the post office.
A. How far B. How often
C. How soon D. How long
Air pollution is becoming than ever before, so many families prefer to buy electric cars。
A. serious B. more serious
C. more seriously D. the most seriously
The manager’s voice sounded on the phone. He offered to show us around the company.
A. softly B. friendly
C. gently D. seriously
Mum told me that I be afraid of the difficulties and should learn to be brave。
A. did not need B. need not to
C. need not D. not need
most of the earth’s surface is covered with water, fresh water is very rare and precious.
A. Since B. While
C. Because D. Although
