11.
Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it ?

_ a _ b _ abaa _ bab _ abb

12.
Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it ?

abca _ bcaab _ ca _ bbc _ a

13.
Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it ?

_ tu _ rt _ s _ _ usrtu _

14.
Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it ?

_ _aba _ _ ba _ ab

15.
Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it ?

c _ bbb _ _ abbbb _ abbb _

16.
Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it ?

_ bbca _ bcca _ ac _ a _ cb

17.
Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it ?

a _ bbc _ aab _ cca _ bbcc

18.
Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it ?

ac _ cab _ baca _ aba _ acac

19.
Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it ?

_ aa _ ba _ bb _ ab _ aab

20.
Which one set of letters when sequentially placed at the gaps in the given letter series shall complete it ?

c _ bba _ cab _ ac _ ab _ ac