—What are on show in the museum?  

—Some photos_________ by the children of Yushu, Qinghai.   [ ]

A. have been taken      

B. were taken  

C. are taken              

D. taken

在进程创建时先赋予进程一个初始优先数，以后在进程运行过程中不断修改优先数，用这种方法设置的优先数称为 【7】 。