$1$ There are several statements about OS listed in the following, and which statements are correct? $(20\%)$

$($a$)$ Disk can be subdivided into several partitions, but the one partition can contain only one disk.

$($b$)$ In Shared lock, several processes can read and write the same file.

$($c$)$ The segment mechanism can be used to solve External Fragmentation problem.

$($d$)$ Suppose the file can provide the Direct Access, the file is fixed length with the logical records.

$($e$)$ The solution to Critical$-$Section Problem should contain these characters: Mutual Exclusion, Progress, and Preemptive.

$($f$)$ Deadlock can arise if four conditions hold simultaneously. These conditions are Mutual exclusion, Hold and Wait, No preemption and Circular wait.

$($g$)$ If a system is in unsafe state, the system has a deadlock.

$($h$)$ Disks or partitions can be RAID protected against failure.

$($i$)$ A file system must be mounted at a mount point before it can be accessed.

$($j$)$ Based on the Demand Paging, the loader will never bring a page into memory unless pa will be needed.

$($k$)$ Copy$-$on$-$Write allows both parent and child processes to initially share the same pages