In both sign-magnitude and $1$'s complement, all patterns starting with $0$ represent positive numbers in the same way.
So, all patterns from $00000000$ to $01111111$ have the same value in both systems.
Number of such patterns is:
$2^7=128$
Now consider patterns starting with $1$.
In sign-magnitude, the remaining $7$ bits directly give the magnitude.
In $1$'s complement, the negative value is found by complementing the bits.
So, negative patterns do not represent the same values in both systems.
Therefore, only the $128$ patterns starting with $0$ have the same decimal value.
Answer: C
