问题 填空题

天然水中含有的部分杂质如下表所示:

溶  解  物  质悬浮物质
主要气体主要离子生物生成物细菌、藻类及原生物、泥沙、黏土等
氧气

二氧化碳

硫化氢等

钙离子、氯离子、

硫酸根离子

镁离子

NH4+、NO2-

HPO42-、Fe3+

H2PO4-

请根据上表内容回答:

(1)写出“主要气体”中一种气体的化学式______;

(2)写出“主要离子”中一种阳离子的符号______.

答案

(1)氧气、二氧化碳、硫化氢的化学式分别是O2、CO2、H2S;

(2)钙离子、氯离子、硫酸根离子、镁离子中钙离子和镁离子属于阳离子,钙离子可以表示为Ca2+,镁离子可以表示为Mg2+

故答案为:(1)O2;(2)Ca2+

单项选择题 A1型题
单项选择题

Although there are many skillful Braille readers, thousands of other blind people find it difficult to learn that system. They are thereby shut (1) from the world of books and newspapers, having to (2) on friends to read aloud to them.

A young scientist named Raymond Kurzweil has now designed a computer which is a major (3) in providing aid to the (4) .His machine, Cyclops, has a camera that (5) any page, interprets the print into sounds, and then delivers them orally in a robot-like (6) through a speaker. By pressing the appropriate buttons (7) Cyclops’s keyboard, a blind person can "read" any (8) document in the English language.

This remarkable invention represents a tremendous (9) forward in the education of the handicapped. At present, Cyclops costs $ 50,000. (10) , Mr. Kurzweil and his associates are preparing a smaller (11) improved version that will sell (12) less than half that price. Within a few years, Kurzweil (13) the price range will be low enough for every school and library to (14) one. Michael Hingson, Director of the National Federation for the Blind, hopes that (15) will be able to buy home (16) of Cyclops for the price of a good television set.

Mr. Hingson’s organization purchased five machines and is now testing them in Maryland, Colorado, Iowa, California, and New York. Blind people have been (17) in those tests, making lots of (18) suggestions to the engineers who helped to produce Cyclops.

"This is the first time that blind people have ever done individual studies (19) a product was put on the market," Hingson said. "Most manufacturers believed that having the blind help the blind was like telling disabled people to teach other disabled people. In that (20) , the manufacturers have been the blind ones.

8()

A.visual

B.printed

C.virtual

D.spoken