矿井瓦斯等级分三类，不正确的等级分类是（）。
A.低瓦斯矿井
B.高瓦斯矿井
C.煤（岩）与瓦斯突出矿井
D.无瓦斯矿井
参考答案：D
—The cost of food and clothing is going up nearly every day.
—Yes, the price of vegetables is much ________ than before. [ ]
A. expensive
B. higher
C. high
D. cheaper
术中异常出血的因素中，与麻醉有关的是（）
A.缺氧
B.干扰凝血过程
C.肌松药
D.动静脉压升高
E.使末梢血管扩张
