urgent

1 There are four statements about OS listed in the following, and which one is correct: (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. 2 There are four statements about OS listed in the following, and which one is correct? ( 5%) (a) The solution to Critical-Section Problem should contain these characters: Mutual Exclusion, Progress, and Preemptive. (b) Deadlock can arise if four conditions hold simultaneous exclusion, Stop and go, No preemption and Circular wait. (c) If a system is in unsafe state, the system has a deadlock. (d) There are two kind semaphores. There are counting semaphore and binary semaphore