Correct ur concept!!
option C is not about ISR is executed after the execution cycle.
It is not that execution cycle, it is a general word that we use in daily routine.
CPU is going to check the interrupt bit after finishing the execution of the current instruction, it means we know that every instruction has to various phases like instruction fetching, decoding, fetch operands, execute, write back . After each phase completes by an instruction not after executing phase then CPU check for interrupts.
There is a big difference between the execution of a current instruction and execute cycle of running instruction...