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进程P1、P2、P3、P4、P5的前趋图如下：

若用PV操作控制进程并发执行的过程，则需要设置4个信号量S1、S2、S3和S4，且信号量初值都等于零。下图中a和b应分别填写(50)，c和d应分别填写(51)，e和f应分别填写(52)。

A.P(S1)和P(S2)
B.P(S1)和V(S2)
C.V(S1)和V(S2)
D.V(S1)和P(S2)

A.shangxuebA.cn/images/ct_csrhsasz20091_crhsaschoosecn_00050(20102)1.jpg'>
B.shangxuebA.cn/images/ct_csrhsasz20091_crhsaschoosecn_00050(20102)2.jpg'>
A.P(S1)和P(S2)
B.P(S1)和V(S2)
C.V(S1)和V(S2)

【参考答案】

C
解析：本题考查的是操作系统进程管理中PV操作方面的基本知识。因为根据题意，进程P3等待P1、P2的结果，因此......

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