In the following question, which one set of letters when sequentially placed at the gaps in the given letter series shall complete it?
a _ bc _ a _ bcdabc _ da _ cd _
acbddb
adbcbd
cabddc
ddcbbc
In the following question, which one set of letters when sequentially placed at the gaps in the given letter series shall complete it?
a _ bc _ a _ bcdabc _ da _ cd _