A disk scheduling mechanism in an operatingsystem causes the disk arm to sweepback and forth across the disk surface servicing all requests in its path. This is a

A．First Come First Serve

B．Shortest Seek Time First

C．Scan

D．None of the above

急进性肾小球肾炎最突出的临床表现是

A．脓尿
B．高血压
C．进行性少尿、无尿
D．血尿
E．水肿