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ACCorDing to thE proFEssor, why is thErE no pErFECt FrAmE oF rEFErEnCEA．sCiEntists hAvE BEEn unABlE to FinD onE.
B．nothing CAn movE FAstEr thAn light.
C．EvErything is in motion.
D．thErE ArE An EnDlEss numBEr oF possiBlE onEs.