Final answer:
A portable radio is the device that may be used to speak to medical control with the least risk of someone hearing the conversation.
Step-by-step explanation:
The device that may be used to speak to medical control with the LEAST risk of someone hearing the conversation is a portable radio.
When it comes to communication devices, a portable radio is often considered the most secure option for confidential conversations. Unlike cell phones, which can transmit signals over long distances and can be intercepted or overheard, a portable radio has limited transmission range and is less likely to be intercepted by unauthorized individuals. Therefore, a portable radio provides the least risk of someone hearing the conversation.