The eastern bluebird is considered the most attractive bird native of North America by many bird-watchers.

You shouldn’t criticize him in front of his friends. It was insensitive of you.

The teacher asked him why hadn’t he done his homework, but he said nothing.

Little he knows about the surprise that awaited him.

Unless there had been a heavy storm, the climbers will not have died.

Oxygen plays a important role in maintaining live.

Ralph wishes that he went to the bank this morning before he went to work.

By measuring the color of a star, astronomers can tell how hot is it.

For thousands of years, man has created sweet-smelling substances from wood, herbs and flowers and using them for perfumes or medicine.

The telephone rang several times and then stop before I could answer it.

The Games' organizers faced significant bed shortages because the record number of more than 13,000 athletes and officials who attended the 2006 Games

Some species of bats are dormant each days and active every night.

Society uses such human emotions as proud, shame, guilt, and fear to maintain itself.

Each of the nurses report to the operating room when his or her name is called.

Narcissus, a character in mythology, gazed at his own image in a pool so ardently that he fell into itself and downed.

By the mid-nineteenth century, land was such expensive in large cities that architects began to conserve space by designing skyscrapers.

Increasing involvement in agriculture by large corporations has resulted in what is known as agribusiness-that is, agriculture with business techniques, including heavy capitalization, specialization of production, and to control all stages of the operation.

Little have people done to alleviate the sea pollution caused by the factories in central Vietnam, haven’t they?

The harder he tried, the worst he danced before the large audience.

The shopkeeper warned the boys don't learn their bicycles against his windows.

There are many reasons why a particular species may become endangering.