A:①②
B:②③
C:③④
D:②④
小明在做实验时,发现一瓶瓶口已敞开不知多久的氢氧化钠溶液(以下简称试液)。联想到药品保存注意事项,小明利用提供的试剂(CaC12溶液、盐酸、CaCO3固体、酚酞)对试液是否变质展开了探究。
他首先的猜想是:试液没有变质,溶液的溶质还是NaOH。小明通过查阅资料得知Na2CO3呈碱性。他根据自己的猜想设计的实验方案是:取少量试液加入试管,滴入酚酞,观察到试液变红。由此得出的结论是原试液没有变质,溶质还是NaOH。
they, take, cry, go, sleep
After finishing all the food in the little bowl,Goldilocks wanted to rest.She chose the small chair,but it was in pieces.Then she walked into the bedroom and very soon fell____in the small bed.The Bears returned to____house.Baby Bear pointed at Goldilocks and____,"That's the bad girl.She ate my food and broke my chair!"Hearing this.Goldilocks jumped up and hurried out of the house without____her basket.She decided not____for a walk in the forest again.
丁零零,闹钟响了。元元打了个哈欠,翻了个身,心想:再睡一分钟吧!就睡一分钟,不会迟到的。