试述生长期修剪的技术措施

The comprehension passages on this course are designed to help you increase your speed. A higher reading rate, with no loss of comprehension, will help you in other subjects as well as English, and the general principles apply to any language. Naturally, you will read every book at the same speed. You would expect to read a newspaper, for example, much more rapidly than a physics or economics textbook but you can raise your average reading speed over the whole range of materials you wish to cover so that the percentage gain will be the same whatever kind of reading you are concerned with.

The reading passages which follow are all of an average level of difficulty for your stage of instruction.

If you get to the point where you can read books of average difficulty at between 40 and 50 w.p.m. with 70% or more comprehension, you will be doing quite well, though of course any further improvement of speed with comprehension will be a good thing.

When you practice reading with passages shorter than book length, do not try to take in each word separately, one after the other. It is much more difficult to grasp the broad theme of the passage this way, and you will also get stuck on individual words which may not be absolutely essential to a general understanding of the passage. It is a good idea to skim through the passage very quickly first (say 500 words in a minute or so) to get the general idea of each paragraph. Titles, paragraph headings and emphasized words (underlined or in italics) can be a great help in getting this skeleton outline of the passage.

Which of the following statements is TRUE according to the passage().

A. You are expected to read various kinds of materials at the same rate.

B. A great deal of specialized knowledge is required to read books of general interest.

C. Titles, introduction and paragraph heading are of great help for grasping the overview of the text.

D. It is less likely that you can raise your average reading rate over the whole range of materials you wish to cover within a short time.

设有下 * * 个关系S，C，SC，它们的主码分别是S#，C#，(S#，C#) S(S#,SName) C(C#,CName) SC(S#,C#,Grade) 下列关于保持数据库完整性的叙述中，不正确的是( )。

A．向关系SC插入元组时，S#和C#都不能是空值(NUL

B．可以任意删除关系SC中的元组

C．向任何一个关系插入元组时，必须保证该关系主码值的唯一性

D．可以任意删除关系C中的元组

双道命令系统特点最突出的企业法律事务组织模式是（）。

A．集中模式

B．分散模式

C．混合模式

D．简单模式

根据功能财政的基本思想，政府需维护财政收支平衡。

新鲜血（7天内的血）主要用于：（）

A.新生儿，特别是早产儿需要输血或换血者。

B.严重肝肾功能障碍需要输血者。

C.严重心肺疾患需要输血者。

D.因急性失血而持续低血压者。

E.弥散性血管内凝血需要输血者。