Whencarbonisaddedtoironintheproperproportions,theresultissteel.
A、containerBats fly, rather than glide, and thus are the only mammals capable of true flight.
Although the Carbon 14 method of dating old objects is not foolproof , it is the best method available at present
People who do not sleep enough tend to become irritable .
InthenortheasternUnitedStates,itrainsintermittently间歇地throughoutthespring.
The Salk vaccine is a major factor in the fight to eradicate polio.
