从仪表控制图PI图中查得管子的口径是什么？（）
A.内径
B.外径
C.内径与外径的平均值
D.中径
参考答案：A
The computer centre, _______ last year, is very popular among the students in this school. [ ]
A. open
B. opening
C. having
D. opened
表演者对其表演享有什么样的权利？
