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

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

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

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. 

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

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. 

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