Under what circumstances may a juvenile choose not to participate in a line-up?

The correct answer is based on the understanding of a juvenile's rights in legal proceedings. A juvenile may choose not to participate in a line-up if it is not specifically ordered by the court for that case. This highlights the legal protections in place for juveniles, ensuring that they cannot be compelled to participate involuntarily without judicial oversight.

In circumstances where a court order is absent, the juvenile maintains control over their participation in such identification procedures. This is vital as it protects their rights and ensures the integrity of the process. The court's involvement serves to uphold the legal standards required for such actions, ensuring that any line-up conducted is justified and appropriate.

Other options do not accurately represent the legal framework surrounding a juvenile's participation in a line-up. For instance, simply not being charged with a crime does not directly exclude them from being involved in identification processes related to investigations. Likewise, while the presence of parents can be an important factor in supporting a juvenile’s rights, their absence alone does not grant the juvenile the right to refuse participation. Lastly, the notion that they could only refuse during a holiday does not hold any legal validity in this context.