The weather in Beijing is colder than in Guangzhou.

e been living in the United States for 20 years, but seldom ________ so lonely as now.

In a new study of African elephants，researchers havefour distinctcharacters that are among a group

If we use the new recycling method, a large number of trees _____.[ ]

Smoking is one of the________causes of cancer, killing millions of people each year. [ ]