Find the missing number?

Answer: Option D

Split the diagram into two halves vertically, consisting of 2 columns of 2 squares each.

And read each 2 adjoining squares as a complete 2 digit number. Numbers follow the sequence of multiples of 7, subtracting 1 each time.

14 - 1 = 13
21 - 1 = 20
28 - 1 = 27
35 - 1 = 34
42 - 1 = 41
49 - 1 = 48
56 - 1 = 55
So,

63 - 1 = 62.
Missing element = 2.