Q. Consider the sequence AB_CC_A_BCCC_BBC_C that follows a certain pattern. Which one of the following completes the sequence?

Explanation : 

1. Mark the blanks with underscores:
AB _ CC _ A _ BCCC _ BBC _ C
There are 5 blanks at positions 3, 6, 8, 13 and 17.

2. Notice the total length of the filled‐in sequence will be 18 letters. If you cut it into six consecutive blocks of 3 letters each, the pattern emerges. Label the blocks by their letter‐positions:

Block 1 = positions 1–3 = A B _
Block 2 = positions 4–6 = C C _
Block 3 = positions 7–9 = A _ B
Block 4 = positions 10–12 = C C C
Block 5 = positions 13–15 = _ B B
Block 6 = positions 16–18 = C _ C

3. The sequence of blocks follows the simple alternating pattern:
ABB, CCC, ABB, CCC, ABB, CCC

4. Fill each blank so each block matches that pattern:

– Block 1 “A B _” must be “A B B” ⇒ blank 3 = B
– Block 2 “C C _” must be “C C C” ⇒ blank 6 = C
– Block 3 “A _ B” must be “A B B” ⇒ blank 8 = B
– Block 4 is already “C C C” (no blank)
– Block 5 “_ B B” must be “A B B” ⇒ blank 13 = A
– Block 6 “C _ C” must be “C C C” ⇒ blank 17 = C

5. Reading the five blanks in order gives B, C, B, A, C – that is option (c).

Thus the completed sequence is
ABB CCC ABB CCC ABB CCC
which clearly shows the alternating ABB/CCC pattern.