Final answer:
To locate Joe's lost mobile device, enabling GPS location services is the most effective option as it can track the device's location via satellites. Other options like IMAP settings, gyroscope, and SSL services do not pertain to device tracking.
Step-by-step explanation:
To assist Joe, the Chief Executive Officer, in finding his lost mobile device, the most effective option would be C. GPS location services. This technology allows for tracking the location of a mobile device using satellites. Enabling GPS location services on Joe's mobile device will require setting it up so that when the device is connected to the internet, he or his assistant can log into a device finder service provided by the mobile operating system or a third-party application and see the device's location on a map.
Options A, B, and D are not the correct choices for this purpose. IMAP settings are related to email configuration and would not help in finding a lost device. A gyroscope is a sensor in mobile devices that helps to determine orientation but does not provide location services. Enabling SSL services secures internet communications and also would not assist in locating a lost mobile device.