A device employing INTR line for device interrupt puts the CALL instruction on the data bus
This line means when a interrupt request signal( INTR ) is enabled then microprocessor has to enable that interrupt .
It receives high INTR signal and activates INTA' signal, So another request can’t be accepted ( put on CALL ) till CPU is busy in servicing interrupt .
INTR is an interrupt request signal it's full form is Interrupt Request .
It has the lowest priority among the interrupts. INTR can be enabled or disabled by using software. Whenever INTR goes high the microprocessor completes the current instruction which is being executed and then acknowledges the INTR signal and processes it.
The INTA' signal means interrupt acknowledge signal .
Once an instruction is completed the processor sends an acknowledgement signal INTA'. ( which mean i have acknowledged your interrupt , wait till i will provide you a service )
Whenever the microprocessor receives interrupt signal. It has to be acknowledged. This acknowledgement is done by INTA’.
So whenever the interrupt is received, INTA’ goes high.
Once the new instruction is received the processor saves the address of new instruction into the STACK and an interrupt service subroutine begins.
CALL instruction saves procedure linking information on the stack and branches to the procedure (called procedure) specified with the destination (target) operand .
All that means Option A is correct here .