নিম্নলিখিত ক্রমটিতে এমন কতগুলি 7 রয়েছে, যার ঠিক পরে 9 থাকে এবং ঠিক আগে 5 নেই? 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.