Correct option is B
Given:

Logic: (Multiplication of side of outer figure and inner figure) + 1
In 1st figure:
(5 4) + 1 = 21
In 2nd figure:
(6 4) + 1 = 25
In 3rd figure:
(3 5) + 1 = 1
Similarly, in last figure:
(4 3) + 1 = 13
Thus, the correct option is (b)






