Select the combination of letters that when sequentially placed in the blanks of the given series will complete the series. _bc_efa_cd_fa_c_ef_bc_ef |
abbebdad adbebbad adbebdad addebdad |
adbebdad |
In this series _bc_efa_cd_fa_c_ef_bc_ef adbebdad is the repeated word The complete series is: abcdef / abcdef / abcdef / abcdef
The letter cluster required is adbebdad |