Consider the message queue below and then answer the questions which follow. Head points to

the oldest message in the queue.

Which of the following calls will read message MSG$21$

$($a$)$ msgrcv$($msqid$,$ &msg$,$ msgsz$,-5,0)$

$($b$)$ msgrcv $($msqid$,$ &msg$,$ msgsz$,2,$ IPC$\_$NOWAIT$)$

$($c$)$ msgrcv$($msqid$,$ &msg$,$ msgsz$,-2,0)$

$($d$)$ All of the above

$($e$)$ None of the above

Which of the following calls will block?

$($a$)$ msgrcv$($msqid$,$ &msg$,$ msgsz$,2,0)$;

$($b$)$ msgrcv $($msqid$,$ &msg$,$ msgsz$,1,$ IPC$\_$NOWAIT$)$

$($c$)$ msgrcv$($msqid$,$ &msg$,$ msgsz$,0,0)$

$($d$)$ msgrcv$($msqid$,$ &msg$,$ msgsz$,-5,0)$

$($e$)$ None of the above

What message will this call receive: msgrcv$($msqid$,$ &msg$,$ msgsz$,0,$ IPC$\_$NOWAIT$)$

$($a$)$ MSG$6$

$($b$)$ MSG$21$

$($c$)$ MSG$1$

$($d$)$ The call will return an error, and message will be received

$($e$)$ None of the above