求解og404页130.132题

看了几遍还是不能理清这篇文章最后一段的逻辑，所以130和132题不知道做。
LineAll the cells in a particular plant start out with
the same complement of genes. How then can
these cells differentiate and form structures as
different as roots, stems, leaves, and fruits? The
(5) answer is that only a small subset of the genes in a
particular kind of cell are expressed, or turned on,
at a given time. This is accomplished by a complex
system of chemical messengers that in plants
include hormones and other regulatory molecules.
(10) Five major hormones have been identified: auxin,
abscisic acid, cytokinin, ethylene, and gibberellin.
Studies of plants have now identified a new class of
regulatory molecules called oligosaccharins.
Unlike the oligosaccharins, the five well-known
(15) plant hormones are pleiotropic rather than specific;
that is, each has more than one effect on the
growth and development of plants. The five have
so many simultaneous effects that they are not
very useful in artificially controlling the growth of
(20) crops. Auxin, for instance, stimulates the rate of
cell elongation, causes shoots to grow up and roots
to grow down, and inhibits the growth of lateral
shoots. Auxin also causes the plant to develop a
vascular system, to form lateral roots, and to
(25) produce ethylene.
The pleiotropy of the five well-studied plant
hormones is somewhat analogous to that of certain
hormones in animals. For example, hormones from
the hypothalamus in the brain stimulate the anterior
(30) lobe of the pituitary gland to synthesize and release
many different hormones, one of which stimulates
the release of hormones from the adrenal cortex.
These hormones have specific effects on target
organs all over the body. One hormone stimulates
(35) the thyroid gland, for example, another the ovarian
follicle cells, and so forth. In other words, there is a
hierarchy of hormones.
Such a hierarchy may also exist in plants. Oligo-
saccharins are fragments of the cell wall released
(40) by enzymes: different enzymes release different
oligosaccharins. There are indications that pleiotropic
plant hormones may actually function by activating
the enzymes that release these other, more specific
chemical messengers from the cell wall.
130.The passage suggests that which of the following is a
function likely to be performed by an oligosaccharin?
(A)To stimulate a particular plant cell to become
part of a plant’s root system
(B)To stimulate the walls of a particular cell to
produce other oligosaccharins
(C)To activate enzymes that release specific
chemical messengers from plant cell walls
(D)To duplicate the gene complement in a particula
plant cell
(E)To produce multiple effects on a particular
subsystem of plant cells
132.According to the passage, which of the following best
describes a function performed by oligosaccharins?
(A)Regulating the daily functioning of a plant’s cells
(B)Interacting with one another to produce different
chemicals
(C)Releasing specific chemical messengers from a
plant’s cell walls
(D)Producing the hormones that cause plant cells
to differentiate to perform different functions
(E)Influencing the development of a plant’s cells by
controlling the expression of the cells’ genes