Which example of research with prisoners would be allowable under the regulations?

The chosen example of examining age at first arrest as a predictor of adult criminal history is allowable under regulations governing research with prisoners because it does not involve manipulations or risks that arise from interventions or treatments applied to the prisoners themselves. This type of research can be considered observational and does not subject the participants to additional risks related to their incarceration.

Research involving prisoners is subject to strict regulations to protect this vulnerable population from undue risk and coercion. Studies must either be aimed at understanding the prison population itself or must focus on treatments or interventions that could benefit them directly. In this case, analyzing historical data about age at first arrest aligns with those guidelines, as it is primarily retrospective and observational in nature.

The other examples involve either direct interventions, manipulation of the prisoners' environments, or may not adhere to specific ethical guidelines that prioritize the safety and well-being of prisoners, making them less likely to be considered allowable under the given regulations.