The best answer for the example question is:
A is the best answer. The parent should be informed of the mistake immediately so that they are aware the baby has not received the immunization and can make appropriate arrangements.
D is the next best answer. The need to repeat the immunization is addressed, however this does not share with the parents what has happened or the reason for the appointment and so is not such a good answer.
C is the next best answer. It is good to fill in a critical incident form so that the causes of the error are investigated but this does not address the need to repeat the immunization.
B is not a good response because it does not address the baby's need and it would be better to discuss the error directly with the nurse to find out what happened.
E is not a good response because you are the only person who knows the baby has not received the immunization and if you take no action this will not be redressed.
Please note: This is an example of how the question might be marked. The scoring framework will be piloted as part of the SJT development to explore the best way of scoring candidates in a granular way.