The pattern in the sequence involves the numbers 2, 3, 4, 5, and 6 in the second and fourth positions, while the first and third positions (B and D) remain fixed.
The missing term must logically continue the pattern, with 3 in the second position and C in the third.
Thus, the missing term is BC3D.

Arun’s present age in years is 40% of Barun’s. In another few years, Arun’s age will be half of Barun’s. By what percentage will Barun’s age increase during this period?