题干

某化学小组在课外活动时做了一个实验,在甲试管中装入某固体物质,乙试管装入某溶液,按如图所示组装好仪器(图中铁架台等仪器已略去).打开止水夹,同时通过分液漏斗加入足量稀盐酸,看到乙试管溶液中有气泡冒出,一段时间后,再关闭止水夹,发现乙中溶液变白色浑浊.符合此实验现象的一组试剂是(    )

选项

甲中固体

乙中溶液

A

CaCO3

Ca(OH)2

B

CuCO3

NaOH

C

Mg

AgNO3

D

KOH

BaCl2

A:A

B:B

C:C

D:D

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答案(点此获取答案解析)

C

同类题1

完型填空

话题

体裁

词数

难度

建议用时

3D技术

说明文

245

★★★

5分钟

      The 30th Olympic Games took place in London from July to August in 2012. Luckily, Chinese 1 fans could watch the exciting games in 3D on TV.

     When you watch 3D movies or TV, you have to wear a(n) 2  pair of glasses. The 3D glasses make the pictures from the screen 3they are there in the room with you.

      3D means having three dimensions(维度): width, height and depth. 3D technology is similar to the way that the human brain and eyes work.   4 the pupils(瞳孔) of a person’s eyes are about 6. 5 cm apart, when we look at something, each eye sees it from a different angle (角度). Our eyes 5 the two pictures to our brain, and the brain puts them together. The small 6 between the picture from the right eye and the picture from the left eye allows us to see depth(立体感).

     When we 7 pictures in two dimensions, each eye gets the same information. That is because the picture has no real depth, and there is only one way of looking at it. A 3D movie or TV needs two film projectors(放映机). One projects a left eye picture and the other projects a right eye picture. The 3D glasses allow us to see  8picture in each eye.

      While one 93D films, he feels that he is actually in the same environment as the things he’s watching. 10 , it also has its disadvantages. People with eye problems may get headaches if they spend too much time watching 3D movies.