在制作临时装片，在盖上盖玻片时，要将盖玻片的一端先接触液滴，然后再缓缓盖下．这样操作的目的在于（  ）

关于放射性元素的半衰期，下列说法中正确的是（   ）

Maybe they are not in the library.(同义句转换)
They____in the library..
Dick is watching Tv now.(用sometimes改写句子)
Dick____ sometimes.
____ I believe chickens can swim.(改为否定句)
I                  chickens        swim.
____ They did it two days ago.(对划线部分提问)
                       they       it?
I eat junk food two or three times a week.( 对划线部分提问) 
____ do you eat junk food?
To sleep for eight hours every night is important.( 同义句转换)
____ to sleep eight hours every night.
____ You should eat some Chinese medicine.(改为否定句)
You          eat         Chinese medicine.
____ The boy didn’t stand up before the teacher came in.( 同义句转换)
The boy         stand up          the teacher came in.
she, what, doing, vacation, is, for, week, next?(连词成句)
____ ？

某校生物兴趣小组在探究“溶液浓度的大小对植物吸水的影响”时，利用新鲜的萝卜、浓盐水、清水等实验材料，按如图所示进行实验．请据图回答：