A possible effect of an error during transcription is the wrong amino acid chain, will be produced.
Option D
The "wrong amino acid chain", will be produced as a possible effect of an error during transcription. A mutated set of proteins will start getting produced. They will have different or faulty functioning. In some cases, they won't have any functions of their own.
To avoid the possibility of an error, the transcript goes through a process of proofreading which further eliminates the chances of a wrong protein being developed.