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Question

Select the combination of letters that when sequentially placed in the blanks will create a repetitive pattern.

_baa_aa_aab_

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
abba

The question asks us to find a sequence of letters that, when placed in the blanks of $_baa_aa_aab_$, creates a repeating pattern.

Identifying the Repetitive Pattern

Let's analyze the template: $_baa_aa_aab_$. There are four blanks.

We need to test the options to see which one forms a clear repetitive sequence when inserted.

Testing Option A: abba

Let's insert the letters 'a', 'b', 'b', 'a' into the blanks sequentially:

  • Blank 1: a
  • Blank 2: b
  • Blank 3: b
  • Blank 4: a

Inserting these into the template $_baa_aa_aab_$ gives:

$a$baa$b$aa$b$aab$a$

Combining these parts results in the sequence: $abbaabbaabba$.

This sequence, $abbaabbaabba$, clearly shows a repetitive pattern. The unit $abba$ repeats three times.

Conclusion

Since inserting 'abba' creates a consistent repetitive pattern ($abba$ repeated), it is the correct combination.

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