ఈ కింది క్రమంలో వెనువెంటనే 9 అంకె ఉండి, ముందు 5 అంకె ఉండకుండా ఎన్నిసార్లు 7 అంకె వస్తుంది? 5 1 7 9 9 7 5 9 8 7 8 7 9 5 7 9 A. 6 B. 1 C. 2 D. 4

Look at every 7 followed by 9 in 5 1 7 9 9 7 5 9 8 7 8 7 9 5 7 9. The 3rd number (7) is followed by 9 and preceded by 1, so it counts. The 12th number (7) is followed by 9 and preceded by 8, so it counts. The 15th number (7) is followed by 9 but preceded by 5, so it does not. That makes 2.