456.Which of the following is true about job chains?
A. They consist of one or more Scheduler programs.
B. They are used to implement dependency scheduling.
C. They are used to implement time-based scheduling.
D. They are used to implement event-based scheduling.
E. None of the above.
Answer: B
答案解析：
参考：http://docs.oracle.com/cd/E11882_01/server.112/e25494/scheduse.htm#ADMIN10021
Creating and Managing Job Chains
A job chain ("chain") is a named series of tasks that are linked together for a combined objective. Chains are the means by which you can implement dependency based scheduling, in which jobs are started depending on the outcomes of one or more previous jobs.