00年1月阅读26题，困惑中

mutegirl

Questions 23-33

The mineral particles found in soil range in size from microscopic clay particles

to large boulders. The most abundant particles—sand, silt, and clay—are the focus

of examination in studies of soil texture. Texture is the term used to describe the

line composite sizes of particles in a soil sample, typically several representative handfuls.

(5)  To measure soil texture, the sand, silt, and clay particles are sorted out by size and

weight. The weights of each size are then expressed as a percentage of the sample

weight.

In the field, soil texture can be estimated by extracting a handful of sod and

squeezing the damp soil into three basic shapes; (1) cast, a lump formed by squeezing

(10) a sample in a clenched fist; (2) thread, a pencil shape formed by rolling soil between

the palms; and (3) ribbon, a flatfish shape formed by squeezing a small sample between

the thumb and index finger. The behavioral characteristics of the soil when molded into

each of these shapes, if they can be formed at all, provides the basis for a general

textural classification. The behavior of the soil in the hand test is determined by the

(15) amount of clay in the sample. Clay particles are highly cohesive, and when dampened,

behave as a plastic. Therefore the higher the clay content in a sample, the more refined

and durable the shapes into which it can be molded.

Another method of determining soil texture involves the use of devices called

sediment sieves, screens built with a specified mesh size. When the soil is filtered

(20) through a group of sieves, each with a different mesh size, the particles become

grouped in corresponding size categories. Each category can be weighed to make a

textural determination. Although sieves work well for silt, sand, and larger particles,

they are not appropriate for clay particles. Clay is far too small to sieve accurately;

therefore, in soils with a high proportion of clay, the fine particles are measured on the

(25) basis of their settling velocity when suspended in water .Since clays settle so slowly,

they are easily segregated from sand and silt. The water can be drawn off and

evaporated, leaving a residue of clay, which can be weighed.

26. It can be inferred mat the names of the three

basic shapes mentioned in paragraph 2 reflect

(A) the way the soil is extracted

(B) the results of squeezing the soil

(C) the need to check more than one

handful

(D) the difficulty of forming different

shapes

这个题目我选的a 答案是b，大家帮我看看吧，谢谢拉

[此贴子已经被作者于2005-7-12 1:13:52编辑过]

爱无伤

In the field, soil texture can be estimated by extracting a handful of sod and

squeezing the damp soil into three basic shapes; (1) cast, a lump formed by squeezing

(10) a sample in a clenched fist; (2) thread, a pencil shape formed by rolling soil between

the palms; and (3) ribbon, a flatfish shape formed by squeezing a small sample between the thumb and index finger.

我觉得此处是先 extracting a handful of sod 然后再squeezing the damp soil (a handful of sod )成三种形状：cast，thread， ribbon.

mutegirl

thanks

ETS你在想什么

今天正好做到这里,呵呵.谢谢.这题,我也错了.