As a security analyst for a smart home devices manufacturer, you are tasked with improving the security of a new line of IoT $($Internet of Things$)$ devices. These devices require robust security measures to prevent unauthorized access and protect user privacy. Which of the following is the MOST critical ssecurity measure focused on direct physical protections of the IoT devices?

A$.$Strong default passwords

B$.$Physical security locks

C$.$Wireless encryption

D$.$Regular firmware updates