下列哪个结构既在上纵隔又在后纵隔？（）
A.食管
B.上腔静脉
C.下腔静脉
D.主动脉弓
E.降主动脉
参考答案：A
We have many differences, but we also have some things ____.
A. in common B. in fact C. as for
办理工作票的”四不开工”是指什么？
