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The self complementary code has an important property which is :

Such codes have the property that the 9’s complement of a decimal number is obtained directly by changing 1’s to 0’s and 0’s to 1’s (i.e., by complementing each bit in the pattern)

And for that we require that the sum of digits of the representation should be equal to 9..

This can be also justified that C) is wrong in the following manner:

The decimal digit '0' can be represented in only way in 5 4 2 0 notation which is :  0 0 0 1 (in binary terms) ..So the 1's complement is : 1 1 1 0..So if we write this in decimal we get 5 + 4 + 2  = 11 which itself exceeds 9 first of all and secondly 9's complement of '0' is '9' but we are getting '11' instead..So it is not a self complementing code..

So option B) only satisfies this property..

Hence B) is the correct answer

answered by Veteran (87.4k points) 15 57 292
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Yes B is only answer, regarding Option C I added 5+4+2+0 as 9 by mistake. so I thought C is also correct Option, thanks for your help and prompt response!

+1 vote