[简答题]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.
To measure soil texture, the sand, silt, and clay particles are sorted out by size andweight. The weights of each size are then expressed as a percentage of the sampleweight.
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 a sample in a clenched fist; (2) thread, a pencil shape formed by rolling soil betweenthe palms; and (3) ribbon, a flatfish shape formed by squeezing a small sample betweenthe thumb and index finger. The behavioral characteristics of the soil when molded intoeach of these shapes, if they can A. A.the way the soil is extracted B.the results of squeezing the soil C.the need to check more than onehandful D.the difficulty of forming differentshapes