学 海 无 涯 UNIT1 CBAD FTFFF achievement literacy proficiency fallen blunty obsolete ineffective completely DAB BADC UNIT2 FFTFT BACD BCAD UNIT3 FTFF CACB BCAD DBADD UNIT4 BBC TTFT CCB DDAB UNIT5 FTFT BCADD CDD CBDC UNIT6 DBBC TFTTF CCAD UNIT7 BCDA FTTFT BCADB UNIT8 TFTFF ADCB BDCD UNIT9 FTTFF BDDA BBAC UNIT10 CB TTFTF BABD BADD UNIT11 BADC BDAC TFFTFF CBAB ACBD UNIT12 FTTFT BDABA ACBA BCDC TEST1 C CDAB C DA C DAD B ADC D DBB BABDB TEST2 A CDAC C AC C BDA A BAB D CAC ADBDC