flash key

how i can get the flash option key in the camera section of block 

when click on the camera in block section the flash key is mission .

how i can get it.

What the Ai2 Camera control can do is here:   http://ai2.appinventor.mit.edu/reference/components/media.html#Camera

After reading the description of the control, you will realize noone can use Ai2 to program the device's camera flash.  When the camera shows up, select it from the options on the camera app.  That is the way this tool works.