Wemust______thattheexperimentiscontrolledasrigidlyaspossible.
Abeamoflightwillnotbendroundcornersunless________(make)todosowiththehelpofareflectingdevice
Tostudyaforeignlanguage,__________.
Herefusedtotelluswhetherhe________(undertake)thejob.
将一枚硬币重复掷n次,以X和Y分别表示正面向上和反面向上の次数,则X和Yの相关系数等于（）
