For storing a negative decimal number in 1's complement representation, just find the binary representation of the decimal number and find the 1's complement by negating it.
Here, 77 in binary can be found out by: $2^7*0+2^6*1+2^5*0+2^4*0+2^3*1+2^2*1+2^1*0+2^0*1$ which is 01001101
For converting fraction .25 to binary, just multiply the fraction by 2 repeatedly, ignoring the whole number part each time as given below:
$0.25*2=0.5$
$0.5*2=1.0$ We stop, beacause the fractional part has reached 0.
Writing down the whole number parts, we get 01
Therefore, the binary of 77.25 is 01001101.01000... (Any number of trailing zeros doesn't matter)
For any decimal number x, negating its binary representation yields binary representation of -x in 1's complement representation.
Therefore, --77.25 is 10110010.1011 (Any number of trailing 1's doesn't matter)
Answer is (c).
