下面对作业控制块JCB表述错误的是( )。
A．JCB是作业存在的唯一标志
B．JCB内容是作业调度的依据
C．JCB只有在该作业退出系统时才清除
D．JCB在作业建立后就不再改变
参考答案：D
解析： 系统为每个作业建立一个JCB。JCB在作业运行期间始终存在，内容不断变化，当作业退出系统时清除该作业的JCB，因此JCB是作业存在的标志。JCB的内容是作业调度的依据。
Please help! Ladies and gentlemen, thank you very much for coming to this concert. I hope you have enjoyed the music. The purpose of this concert is to (1) money for children in Africa. Every day (2) children in Africa die because they have diseases or have not enough (3) . There are two main reasons. First, there are no jobs for the children’s parents, so they have no money to buy food or (4) . Second, the governments in many African countries do not have the money to take care of poor people. Most African countries are poor. The land is not good for (5) food and the weather is also bad for farming. The organization we are trying to help, the Feed Africa Fund, _(6) a lot of money every year on food for poor people in Africa. The money comes (7) people like you kind, generous people who do not want to see children die form hunger. Just one dollar can buy enough rice or corn to (8) a family of four for three days. How much do you spend on food every day? Ten dollars? Twenty dollars? I am sure you can spend a little (9) on your own food so that you have a few dollars for The Feed Africa Fund. Ladies and gentlemen, we will now take a (10) . Please be generous. Thank you.
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