on thE BAsis oF thEir oBsErvAtions, sCiEntists ______.
A．mAkE morE oBsErvAtions
B．DEvElop hypothEsEs AnD thEoriEs,
C．rEvEAl thEir oBsErvAtions to thE puBliC
D．ChAllEngE thEir CollEAguEs