假設(shè)系統(tǒng)有n(n≥5)個(gè)并發(fā)進(jìn)程共享資源R,且資源R的可用數(shù)為2。若采用PV操作,則相應(yīng)的信號(hào)量S的取值范圍應(yīng)為()。A.-1~n-1B.-5~2C.-(n-1)~1D.-(n-2)~2