油雾和()是气动仪表的主要威胁。
A.空气
B.水
C.蒸汽
D.氮气
参考答案:B
规格、型号完全相同的两只新旧白炽灯泡,我们可以通过观察______,把二者区别开来.理由是______.
30 — I’ve been told that the sports meeting might be ______.
— Yes, it all depends on the weather.
A put away B put out C put aside D put off