取压管的粗细、长短应取合适。一般内径为6～10mm，长为3～50m。
参考答案：对
the windows before you leave the classroom. [ ]
A. To close
B. Closing
C. Closed
D. Close
酸性最强的是
A．大黄酚B．大黄素C．大黄素甲醚D．芦荟大黄素E．大黄酸
