Solid geometry has enabled astronomers to calculate the positions of the heavenly bodies relative to one another.

The economy of Dallas, Texas, is strong and diversified .

One of the greatest breakthroughs for professional women came in 1973 when the field of banking opened up for them.

Comets are still regarded with awe by some people.

The Salk vaccine is a major factor in the fight to eradicate polio.

People who do not sleep enough tend to become irritable .

Double Eagle in the first transatlantic balloon, was greeted by avid crowds in France.

Some animals pant and sweat to speed evaporation of body moisture and thus cool themselves.

Some children display an unquenchable 难以抑制的 curiosity about every new thing they encounter.

Food must be moist in order to have a taste.