润滑油的水分不合格原因有（）。
A、添加剂带水
B、调合温度过低
C、油罐底部存水
D、压缩风带水
参考答案：A, C, D
When _____ different cultures, we often pay attention only to the differences without noticing the many
similarities. [ ]
A. compared
B. being compared
C. comparing
D. having compared
原发性肺动脉高压出现胸痛的原因是（）
A.肺实质损伤
B.心肌缺血
C.心力衰竭
D.肺动脉高压
E.肺血栓形成
