Statement I :
Floating point addition is always associative.
I is false because of round off error.
Statement II : Shifting a twos-complement integer right by one bit, and filling from the left with 0, is always equivalent to dividing by 2.
II is false because negative numbers have a leading 1 bit in two’s complement, so the left should be filled with a 1 if the number is negative and a 0 if it is positive.
Statement III An integer’s ones-complement representation is never identical to its twos-complement representation
To compute the one’s complement representation of a negative number, write the number as a positive number but then flip the bits. Transforming this to two’s complement then requires adding 1.
In general, this means that the one’s and two’s complement representations of a negative number differ.
However, for positive integers, the one’s and two’s complement representations are the same, so III is also false.
Hence all three statements are false , option C is correct .