元杂剧的四大悲剧
参考答案：
关汉卿的《窦娥冤》、马致远的《汉宫秋》、白朴的《梧桐雨》、纪君祥的《赵氏孤儿》。
当LKD1-T车站列控中心双CPU比较不一致时系统（），双机切换。
When asked how he liked his job, he said he was happy _____ he was. [ ]
A. what
B. who
C. where
D. how
