问题
问答题
写化学式：硝酸钙______，氢氧化铝______．
答案
硝酸钙中钙元素显+2价，硝酸根显-1价，其化学式为Ca（NO3）2．
氢氧化铝中铝元素显+3价，氢氧根显-1价，其化学式为Al（OH）3．
故答案为：Ca（NO3）2；Al（OH）3．
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写化学式：硝酸钙______，氢氧化铝______．
硝酸钙中钙元素显+2价，硝酸根显-1价，其化学式为Ca（NO3）2．
氢氧化铝中铝元素显+3价，氢氧根显-1价，其化学式为Al（OH）3．
故答案为：Ca（NO3）2；Al（OH）3．
Passage Two
| Running a School Book Stall 开办学校书店 I assume that the desirability of a school book stall needs no urging. Many schools sell food and toys. If we do not sell books it is surely strange Many schools serve areas where book shops do not exist and the only books brought before children for buying are the dubious selections of supermarkets. Moreover even in communities where a good book shop is available the guidance which can be given at the book stall is valuable, as we soon found. Essentially the school book stall is an extension of the encouragement and guidance in private reading which is part of the work of the English teacher. The first essential then, in setting up shop is a teacher particularly interested in children reading and in building up as wide as possible a knowledge of books to suit the school’s range of pupils. Given the teacher, the next requirement is a bookseller willing to supply you. In some cases you will be able to obtain your books on credit, paying as you sell, but if the school can find a sum to purchase its stock, or at least a part of it, this is a great help. Having found your supplier you then approach the Publisher’s Association for a Book Agent’s licence. The licence entitles you to a discount on your purchase through your chosen supplier, the usual discount being 10% with service. Service usually consists of delivery and a sale or return arrangement, the latter essential in allowing you to be enterprising and experimental in your stock. Without service a slightly higher discount is given but the former arrangement is clearly preferable. The biggest, indeed the only considerable, cost in running the book stall is the occasional theft of a book and this may well vary from school to school but the presence of the teacher and the alertness of the assistants is largely deterrent, and the discount should cover this and any other smaller expenses. Browsing is essential. The books must be handled. You cannot keep them safe and immaculate behind glass. For equipment the only essentials are some tables on which to display the books and a cupboard to store them in. Incidentally an arrangement of books with covers rather than spines visible seems to be vastly more attractive and accessible to children who have not the habit of browsing. A single way out past the cash desk is helpful to security and we record details of each purchase including the age of the buyer both for reordering and as interesting information on reading habits. Initially we stocked two hundred titles and the selection has grown to close on a thousand. It is convenient if cash or credit allows you to have duplicate copies of popular titles. What is stocked must depend on the teacher in charge. What you are prepared to sell in the cause of encouraging interest in reading will obviously be an individual judgment. Sales for their own sake are in the school context obviously purposeful and the teacher needs to be able to explain to interested parents why he thought a given book valuable for a certain child. There are always more offers of help from pupils than we can accept. The assistants serve, recommend, order, make posters and arrange displays. Some of the least able pupils have worked devotedly at the book stall. Publicity is vital. We have two display cases on the school approach containing forty books changed fortnightly and they arouse a lot of interest. Teachers’ recommendations, book lists, beginnings of stories read to classes, do much. Some classes buy a book a week between them. The book stall is always open on such occasions as Parent’s Evenings. We open twice a week in the lunch hour and we sell twenty to forty books a week, commercially not much but in our opinion well worth the effort. |
The school makes it possible for the children to know what books are available by______.
A．rearranging all of the books every two weeks
B．arranging fortnightly visits to the book stall
C．exhibiting books to advantage
D．holding regular exhibitions of books