When being photographed, maria used to blink whenever the flash went off. now, maria starts blinking every time she is photographed, even before the camera's flash goes off. to maria, the camera has become a(n) conditioned response (cr) unconditioned response (ur) conditioned stimulus (cs) unconditioned stimulus (ucs)?

Maria's blinking is a response to something - it is her reaction to the flash (blinking protects her eyes from too much light) - but the camera is a stimulus  - the thing that Maria reacts to.

So we know, it will be a stimulus. Now, it will be a conditioned stimulus, because this reaction is learnt and not "natural" (present without learning) - therefore it will be a conditioned stimulus.