Hard
A letter series follows a hidden pattern: ab _ bc _ c _ ba _ c. Which option correctly fills the four blanks in order?
Explanation
Explanation
The sequence is made of four groups of 3 letters, and each group contains exactly one 'a', one 'b' and one 'c'. Group1 (a,b,_) needs c; Group2 (b,c,_) needs a; Group3 (c,_,b) needs a; Group4 (a,_,c) needs b. Reading the blanks in order gives c, a, a, b - that is, 'caab'.
PRO TIP
Re-check your working by substituting the answer back into the original question.