Ans is B
B)is NOT CORRECT as the number of requests for disk service can be greatly influenced by file allocation method.e.g a program reading contiguous allocated file will generate several requests that are closed together on the disk hence minimal head movement . on the other hand linked file or indexed file may include scattered block which need more head movement
C)is TRUE Caching the directories and index blocks in main memory can also help in reducing disk arm movements especially for read operation.
d)is TRUE as SCAN & C-SCAN are less likely to be suffer from starvation as they move in both direction irrespective of type of request. SSTF may suffer from starvation