Final answer:
The legality of an informed consent should be questioned when the healthcare provider fails to disclose potential risks and alternatives before obtaining consent.
Step-by-step explanation:
The legality of an informed consent should be questioned in Option 2: The healthcare provider did not disclose potential risks and alternatives before obtaining consent. Informed consent requires that participants are fully informed about the procedure, including potential risks and implications, before they can give their consent. Failing to disclose this information violates the principle of autonomy and can lead to unethical practices.