The correct option is A 5
For a magic square, numbers in every row, colomn and diagonal add upto the same sum.
Let's add the rows in the square.
1st row = 4 + 3 + 8 = 15
3rd row = 2 + 7 + 6 = 15, thus 15 is our magic sum.
In the second row, we have 9 + 1 = 10. Since the sum of the numbers should be 15,
=> The missing number = 15 - 10 = 5