Q.78 answer = option B
The implementation is incorrect because if two barrier invocations are used in immediate succession the system will fall into a DEADLOCK.
Here's how: Let all three processes make process_arrived variable to the value $3$, as soon as it becomes $3$ previously stuck processes at the while loop are now free, to move out of the while loop.
But for instance let say one process moves out and has bypassed the next if statement & moves out of the barrier function and The SAME process is invoked again(its second invocation) while other processes are preempted still.
That process on its second invocation makes the process_arrived variable to $4$ and gets stuck forever in the while loop with other processes.
At this point of time they are in DEADLOCK. as only 3 processes were in the system and all are now stuck in while loop.