How does the Hardware trigger an interrupt?

A. Sending signals to cpu through a system bus
B. Executing a special program called interrupt program
C. Executing a special program called system program
D. Executing a special operation called system call

Which operation is performed by an interrupt handler?

A. Saving the current state of the system
B. Loading the interrupt handling code and executing it
C. Once done handling, bringing back the system to the original state it was before the interrupt occurred
D. All of the mentioned