问题
选择题
—I have ____ here for two months.
—So you ____ here since two months ago.[ ]
A. come, came
B. been, have been
C. been, come
D. come, have been
答案
答案：C
搜题请搜索小程序“爱下问搜题”
—I have ____ here for two months.
—So you ____ here since two months ago.[ ]
A. come, came
B. been, have been
C. been, come
D. come, have been
答案：C
若用PV操作控制进程P1～P5并发执行的过程，则需要设置5个信号量S1、S2、S3、S4和S5，进程间同步所使用的信号量标注在上图中的边上，且信号量S1～S5的初值都等于零，初始状态下进程P1开始执行。下图中a、b和c处应分别填写（1）；d和e处应分别填写（2），f和g处应分别填写（3）。