Certified Clinical Research Associate (CCRA) Practice Exam

The option indicating that subjects who cannot write can make their mark on the informed consent form is correct because this practice ensures that individuals who are unable to sign their name due to physical or cognitive limitations can still indicate their consent to participate in a study. Making a mark, such as an "X" or another symbol, serves as an acknowledgment of their informed consent when they are unable to provide a traditional signature.

This method respects the autonomy of participants while still adhering to ethical standards within clinical research, which require that consent is obtained in a way that honors the individual's capacity to make decisions. It's also important for the research ethics committees and regulatory bodies to ensure that the subject understands the study's purpose, risks, and benefits, regardless of the media used for consent.

Using a stamp as a signature or having a witness sign for them may not be acceptable in all research settings due to the lack of direct indication from the participant themselves. Leaving the form blank does not fulfill the requirement of obtaining informed consent. Therefore, making their mark is the most appropriate and widely accepted practice for individuals who cannot write.