Both B and C are Wrong.
Range of Unsigned Representation of Binary Numbers: 0 to 2n-1
Range of Signed, 1's complement : -(2n-1-1) to (2n-1 -1)
2's complement Representation of binary number : -(2n-1) to (2n-1 -1)
For eg: take a binary string of length 3
unsigned (max,min) = 111,000 (7,0)
signed (max,min) = 011,111(3,-3)
1's complement(max,min) = 011,100(3,-3)
2's complement(max,min) = 011, 100(3,-4)