combinations大学英语第四册3

2021年1月20日发(作者：普纳)
Passage 3
The “balance of nature” is not an empty phrase. Nature provides a population to occupy a
suitable environment and cuts down surplus population to fit the available food supply. One means
of reducing surplus population is predators(
食肉动物
); others are parasites(
寄生虫
) and diseases.
Also, population density produces nervous disorders and even drivers animals to mass migrations,
like the lemmings(
旅鼠
) of Norway who plunge(
跳入
) into the sea.
That
predators
populations
increase
to
control
other
animals
has
long
been
known.
Many
years ago, the Hudsons Bay Company records revealed that the fox population went up and down
about a year after the rabbit population had gone up and down.
Sometimes a situation occurs in which the predator population is reduced to a level below
that which nature can readily replace. On V
alcour Island in Lake Champlain (New York), a costly
campaign resulted in the elimination of predatory animals only to have birds and small animals
(including grouse(
松鸡
) and hares, popular game) increase for four years afterward. Then, lacking
predator control, nature resorted to disease to cut down these populations.

Jamaica
had
an
example
of
natures
persistence
in
providing
animals
for
existing
habits.
Sugar
planters,
about
75
years
ago,
imported
mongooses(
猫鼬
)
to
control
rats.
The
mongooses
killed off the rats and, with plentiful food, multiplied. Rats became scarce and the mongooses ate
lambs,
kids,
puppies(
小狗
)
，
and
wildlife.
Eventual
ly,
food
became
scarce
and
the
mongooses’
population declined.
phrase “balance of nature” (Line 1, Para. 1) means ____________.

A)
reducing the population of predators
B)
keeping the right number of animals for the right amount of food
C)
keeping the ration of small game to predators
D)
driving animals t mass migrations
fact that number of predators has much to do with that of other animals ______.
A) is not recent knowledge






B) has just been learned
C) has not proved yet











D) is not important now
43. When predators control fails, nature brings animal population into balance by _______.
A) eliminating the number of predators
B) increasing the number of other animals
C) seeping the help of disease to reduce other animals
D) replacing the number of predators immediately
44. When the mongooses in Jamaica killed off the rats they ___________.



A) attacked humans













B) ate the sugar crop



C) became problems themselves



D) had nothing to eat
45. It is implied in the passage that ___________.



A) sugar planter imported mongooses to control rats



B) man should never kill animals



C) man has complete control over nature



D) to upset the balance of nature can be troublesome

Passage 4
It is natural for young people to be critical of their parents at times and to blame them for
most of the misunderstandings between them. They have always complained, more or less justly,