真空蒸发的目的是给蒸发设备造成真空,降低溶液的沸点,增加温度差,使蒸汽过程在真空下完成,提高蒸发效率,降低汽耗。
A. 正确
B. 错误
Texts are usually used in English classes for two main purposes: as a way of developing reading comprehension and as a way of learning new language.()
A. 正确
B. 错误
CO2灭火剂喷射时温度低达()。
A. —48.5℃
B. —18.5℃
C. —78.5℃
吐司面包(白面包)配方,盐的用量约为面粉的()
A. 0%
B. 2%
C. 4%
D. 6%