Which of these statements best explains why p waves arrive earlier than s waves at the seismic station?

a. s waves are generated after p waves arrive at the surface
b. s waves make longer lines on the seismogram than p waves
c. p waves are created first and s waves originate from p waves when they are reflected by solid rocks
d. p waves move straight through all medium and s waves move only through solids in a curvy motion

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.