Explanation : A class can inherit only one Abstract class but may inherit several interfaces. An Abstract class can provide complete and default code but an interface has no code. For more information on Abstract class Refer:Pure Virtual Functions and Abstract Classes in C++ Option (C) is correct.
Explanation : P1 is holding 5 tape drive but it require 10 tape drive, 5 tapes are required for P1. P2 is holding 2 tape drive but it require 4 tape drive, 2 tapes are required for P2. P3 is holding 3 tape drive but it require 9 tape drive, 6 tapes are required for P3. We have total 12 tape out of which 10 are allocated, 2 tape are free. These 2 tape can be allocated to P2. After P2 complete its execution it will free 4 tape, but these 4 tape can not fulfill requirement for P1 or P3. That's why system is in unsafe state. So, option (B) is correct.
Explanation : In Unix operating system, special files are used to provide a mechanism to map physical device to file names. For more information on Unix file system Refer:Operating System | Unix File System Option (B) is correct.