Batsfly,ratherthanglide,andthusaretheonlymammalscapableoftrueflight.
A、straightBatsfly,ratherthanglide,andthusaretheonlymammalscapableoftrueflight.
Thecontrolsofmostmodernairplanescanbeoperatedeithermanuallyorautomatically.
TheSalkvaccineisamajorfactorinthefighttoeradicatepolio.
AlthoughtheCarbon14methodofdatingoldobjectsisnotfoolproof,itisthebestmethodavailableatpresent
TheNativeAmericaninterpreterSacajaweawasavaluablememberoftheLewisanddarkexpeditionin1805.
