A dead giveaway of what?
The battery backup on that type of clock is just that: a battery to preserve the time during a power outage until AC house current is again available, the idea being you won't have to set it if you unplug it and move it somewhere else. While this clock is on battery backup, it's basically dead to the world. It can keep the time, but it can't display it, nor can it alarm.
This gadget needs to be plugged in to work. You can see the AC cord in the photos. Who ever heard of a bomb that needed to be plugged in to explode?
Either accidentally or on purpose, Ahmed (and his dad, either before or after) presented an IQ test to Ahmed's English teacher, who failed abjectly by freaking out, leading to a gift to Obama and the Progressives, who now can point to an innocent oppressed Mooselimb!
The response should have been: That's very interesting, Ahmed. Now put it away until engineering class. (Followed by a politically incorrect email to the principal – watch this wog, his daddy is CAIR!)