– This dress was last year’s style.

– I think it still looks perfect ________ it has gone out of fashion this year.

A．so that

B．as if

C．ever since

D．even though

如果信号量S的初值是5，现在信号量的值是-5，那么系统中的相关进程至少执行了几个P(S)操作与信号量S相关的处于阻塞状态的进程有几个如果要使信号量S的值大于0，应该进行怎样的操作