Which of these statements best explains why models are used to study atoms? atoms of all materials are not the same. atoms cannot be observed with any scientific instrument. atoms are hypothetical particles which do not actually exist. atoms are too small to be examined in detail without a microscope

Consider a file currently consisting of 200 blocks. assume that the file control block (and the index block in the case of indexed allocation) is already in memory. calculate how many disk i/o operations are required for contiguous, linked, and indexed (single-level) allocation strategies, for each of the conditions listed below. in the contiguous-allocation case, assume that there is not room to grow at the beginning but there is room to grow at the end. also assume that the block information to be added is stored in memory.