এই ক্রমে লুপ্ত (?) সংখ্যাটি নির্ণয় করুন: 9, 4, 16, 6, 36, 9, 81, ? A. 12 B. 10 C. 11 D. 13

The series alternates two patterns. Odd terms 9, 16, 36, 81 are squares of 3, 4, 6, 9. Even terms 4, 6, 9, ? increase by 2, 3, then 4, so the next is 9 + 4 = 13.