一定温度下,向质量分数为a的乙腈(CH3CN)溶液中加入等体积水,所得溶液中乙腈质量分数为0.4a,则乙腈的密度(ρ1)与水的密度(ρ2)的关系是( )
A:ρ1>ρ2
B:ρ1=ρ2
C:ρ1<ρ2
D:无法确定
进入青春期后,人体会出现一系列正常的生理现象,如女孩会出现
能吞食大量细菌,对污水有一定净化作用的单细胞生物是( )
(____)A. Orange, orange. Sit down.
(____)B. Black, black. Stand up.
(____)C. White, white. Touch the ground.
(____)D. Brown, brown. Turn around.
(____)E. Red, red. Carry your bag.