如图是某课外活动小组的同学设计的4个喷泉实验方案.下列有关操作不可能引发喷泉现象的是( )
A:挤压装置①的胶头滴管使CCl4全部进入烧瓶,片刻后打开止水夹
B:挤压装置②的胶头滴管使NaOH溶液全部进入烧瓶,片刻后打开止水夹
C:用鼓气装置从装置③的a处不断鼓入空气并打开止水夹
D:向装置④的水槽中慢慢加入足量浓硫酸并打开止水夹
A. You're welcome.
B. What shape would you like?
C. I'd like some cherries, too.
D. What kind of pudding would you like?
E. Yes. I want to buy a pudding.
A: Can I help you?
B:____
A:____
B: I'd like a chocolate pudding.
B: I'd like a heart-shaped pudding.
A: Anything else?
B:____How much are they?
A: 70 yuan.
B: Here is the money.
A: Thank you.
关于光电效应,下列说法正确的是( )