We know that the Divisibility Rule of 3 says that if the sum of the digits are a multiple of 3 or can be divided by 3 then the digit itself can be divided by 3
Now, we're assuming the missing number to be x
So, Sum = 7 + 1 + 5 + x + 4 + 2 + 3 = 22 + x
Now, we'll be verifying all the options
Option A) 0 , then Sum = 22 -----> Discarded as 22 cannot be divided by 3
Option B) 2 , then Sum = 24 -----> Accepted as 24 is a multiple of 3
Option C) 5 , then Sum = 27 -----> Accepted as 27 is a multiple of 3
Option D) 6 , then Sum = 28 -----> Discarded as 28 cannot be divided by 3
Now the question tells us that in the place of x we can only accept the smallest whole number
So, the feasible answer would be 2 i.e option B)