Ababymightshowfearofanunfamiliaradult,_______heislikelytosmileandreachouttoanotherinfant.
A、if_______themovieIwouldhavefinishedmypaperlastSunday.
Wemust______thattheexperimentiscontrolledasrigidlyaspossible.
Human behavior is mostly a product of learning ________ the behavior of animals dependsmainly on instinct.
________,Johnhasbeentoseveralforeigncountries.
We regret to ________ that it may not be possible to deal with every request.
