It is difficult to write rules that tell exactly when we should apologize , and it is not difficult to learn how to do it 

Mercury and alcohol are widely used in thermometers because their volume increases uniform with temperature. 

Ours brains are incredibly agile machines, and it's hard to think of anything they do more efficient than recognize face. 

Parks which are found in downtown areas where office workers and store employees can enjoy their lunch hours sitting on the green grass in clean, fresh air. 

By the turn of the century, most of the inventions that were to bring in all the comforts of modern living has already been thought of. 

Today, although their status varies from country to country, women in most parts of the world have gained  significance legal rights.

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

The Red Cross organizes and leads relief assistance missions after natural disasters such as floods, tsunamis, earthquakes, and homelessness.

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

The freshman failed to follow the advice of her senior that he studied hard and not go out too much. 

Not one in one hundred children exposed to the disease are likely to develop symptoms of it.

The office manager insists that his staff use all of their vacation time, but he hardly never takes a vacation himself.

The developing of the submarine was hindered by the lack of a power source that could propel an underwater vessel

The guide told the tourists that it was a good restaurant specializing in seafood just round the corner from the museum. 

There was a gradual raise in the number of literate males and females in the lowlands.

The clerks who are happy to wait for their customer will get promoted soon.