Look at the Hundreds digit first - it is 4 = 2 + 2
This means A + B + C = 22, right?

No - we must also look at the ones digit - it is 4

Since, 7 + 1 + 6 is 14 - 1 gets carried to Tens digit
Thus A + B + C + 1 must be 22

i.e. A + B + C = 21
C = 21 - 2A (As, A = B)

Plug A = 9 (single digit numbers only)
C = 3

Plug A = 8
C = 5

Plug A = 7
C = 7

We see, on decreasing the value of A or B, C is increasing

The only match we have here is 3
Hence, option C