当大气压力突然降低时，矿山瓦斯涌出量会（）。
A、减少
B、增大
C、可能增大也可能减少
D、无变化
参考答案：B
She told me that she has already gone to the United States four times before she attended that conference.
A. had already been B. has already beenC. already went D. was already going
为了确保测量结果有效、可靠，GB/T19001-2008标准要求对测量设备应实施以下控制（）
A.建立测量设备台帐
B.编制测量设备周检计划
C.按规定的时间间隔或在使用前进行校准和检定
D.以上全部
