测定深静脉是否通畅的试验是()
A.Perthes试验
B.Trendelenburg试验
C.Pratt试验
D.Branham征
E.5P征
参考答案:A
You are given only half an hour to finish your speech on the subject, so you'd better not _____ it too far. [ ]
A. expand
B. extend
C. enlarge
D. increase
控制液空、液氮纯度的要点有哪些?