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.

With lasers scientists can probe many physical processes, such as combustion, once beyond our ken.视野

The flower bud of a water lily 百合 opens at sunset since .its opening is triggered(commence) .by the decreased light.

All living organisms, regardless of their unique identity, have certain biological, chemical, and physical characteristics in common.