Correct answer : (D)
In non-vectored interrupt, it is responsibility of CPU to find the address of ISR and to find the device which caused interrupt.Actually once CPU gets interrupt from a device, it completes its current execution phase and start servicing the interrupt. To do so,CPU first runs a default ISR, address of it is already known to CPU. Now this default service routine is stored somewhere in fixed memory location which CPU knows. So CPU refers to it and find the address of actual ISR from it & also address of the device which caused the interrupt. Actually CPU uses POLLING technique to find address of interrupt causing device.So once CPU gets address of ISR,it starts executing it and after completion it resumes its own execution.