A:胶体粒子直径在1-100nm之间
B:胶体粒子带电荷
C:胶体粒子不能穿过半透膜
D:胶体粒子能够发生布朗运动
若a,b是方程x2+2x-2006=0的两根,则a2+3a+b=()
a.过滤 b.蒸馏 c..萃取 d分液
①分离水和菜籽油的混合物____.②海水淡化____.
— The _____ of July is your birthday. What do you usually do?
— I usually help my mother with some housework because I want her to have a rest _____ that day.