2010年是五四运动91周年,下列最能体现该运动性质的口号是: [ ]
A、“废除二十一条”
B、“拒绝在和约上签字”
C、“外争国权,内惩国贼”
D、“还我山东”
答案:C
Gas masks().
A.should be worn while fighting a fire
B.can be used in atmospheres deficient in oxygen
C.filter contaminants from air that is to be breathed
D.may be substituted for a self-contained breathing apparatus
填料吸收塔流体力学特性实验:取样分析塔底吸收液浓度时,应该注意的事项是什么?