A:The more carefully, the fewer
B:The more careful, the less
C:The more careful, the fewer
D:The more carefully, the less
现有一瓶溶质质量分数为20%的氯化钠溶液200克,要使其质量分数增加一倍,
(1)若采用蒸发溶剂的方法,需要蒸发多少克溶剂?
(2)若采用增加溶质的方法,需要增加多少克溶质?
如图,已知△ABC中,AB∥EF,DE∥BC,则图中相等的同位角有( )
引起传染病的是( )