The correct option is D d
The option that states the part with the error is the correct option.
These parts a, b and c draw a comparison between two individuals 'he' and 'I', where 'he' is as guilty as 'I'. The third part has an elliptical sentence 'I'. An elliptical sentence is a shortened sentence (or just a word) that has words missing in it. These words are implied, and this type of sentence is used to avoid a repetition of similar words in the sentence.
If you expand the sentence, it is: 'He is every bit as guilty as I am.'
Hence, the verb 'am' can be implied and does not have to be included.
The parts do not contain any error. They are grammatically correct and have a complete meaning.
Hence, options A, B and C are all wrong answers.
Option D is correct as it states: NO ERROR