They have not seen him anywhere since last week.

People say that the bridge was destroyed in the war.

As personal incomes grow and vehicles become more affordable, problems associated with pollution have emerged like a major urban issue.

Many years ago, the climate of North America became such cold that great sheets of ice covered most of Canada.

Several developed countries have had a rapid decline in fertility because many women there have delayed to have children.

Error identification

Vietnam faces a challenge which it is the rapid increase of motor vehicles, particularly     in the big cities.

I speak English ______.

It is estimated that the population of Vietnam will reach 100 million for the next 25 years and will stabilize at 120 million by the middle of this century.

Man is damaging the balance of nature which regulates climate and the atmosphere, produces and maintain healthy soils, provides food from the seas.

On the first of next month, John ______ for that computer company for five years.

Those trees ______ last month. Now they ______.

Jennifer and I went to the mall to buy a blender, ______

______ when the earthquake ______ last week?