Grasslands need time to rest when cattle and other animals feed on them．Moving animals from one area of pasture(牧场)to another can provide the time needed for new growth．This is called rotational grazing．(循环放牧)
Rotational grazing is good for the land and the animals, and it can save money．This form of grazing can reduce the need for pesticide(农药)treatments by reducing the growth of weeds．And it can limit the need for chemical fertilizers by letting animal wastes do the job of natural fertilizer．Rotational grazing can even help prevent wildfires by keeping grasslands in good condition．
Letting animals feed continually and intensively(集中地)in the same grazing areas can require costly replanting．Animals eat the most desirable growth first．When that keeps happening, the roots do not have enough time to recover．As a result, less desirable plants may replace them．Intensively used grasslands are also harmed as the soil is continually crushed under the weight of heavy animals．
While rotational grazing can save money over time, it also requires planning．And that starts with a good map to mark fences, water supplies and grazing areas．
Changing methods of grazing also requires time．Farmers may want to put up electric fences to enclose(圈起)grazing areas, called paddocks．The paddocks will need water．Some farmers design a path for animals from different paddocks to drink from a common watering place．
Farmers can start rotational grazing by removing animals from a pasture when the grass is eaten to less that five centimeters．The pasture is then kept empty until the grass grows to more than fifteen centimeters high．
Sheep and goats may require special preparations．They may need stronger fences than other animals．And while they eat the grass, they may need guard animals to protect them from animals that would like to eat them．
(1)
Grasslands won't depend on chemical fertilizers when ________．
[ ]
A．
the soil of grasslands is naturally rich
B．
animal wastes serve as natural fertilizer
C．
rotational grazing can prevent wildfires
D．
grasslands are usually in good condition
(2)
The function of putting up electric fences is to ________．
Our boat floated on, between walls of forest too thick to allow us a view of the land we were passing through, though we knew from the map that our river must from time to time be passing through chains of hills which crossed the jungle plains．Nowhere did we find a place where we could have landed：where the jungle did not actually spread right down into the river, banks of soft mud prevented us going ashore．In any case, what would we have sailed by landing?The country was full of snakes and other dangerous creatures, and the jungle was so thick that one would be able to advance only slowly, cutting one’s way with knives the whole way．So we stayed in the boat, hoping we reached the sea, a friendly fisherman would pick us up and take us to civilization．
We lived on fish, caught with home-made net of string(we had no hooks), and fruits and nuts we could pick up out of the water．As we had no fire, we had to eat everything, including the fish, raw I had never tasted raw fish before, and I must say I did not much enjoy the experience; perhaps sea fish which do not live in the mud are less tasteless．After eating my raw fish, I lay back and dreamed of such things as fried chicken and rice, and ice-cream．In the never-ending damp heat of the jungle, ice-cream was a particularly frequent dream．
As for water, there was a choice：we could drink the muddy river water, or die of thirst．We drank the water．Men who had just escaped what had appeared to be certain death lose all worries about such small things as diseases caused by dirty water．In fact, none of us suffered from any illness as a result．
One day we passed another village, but fortunately nobody saw us．We did not wish to risk being taken prisoners a second time：we might not be so lucky to escape in a stolen boat again．
(1)
What they could see in the boat was only ________．
[ ]
A．
high wall
B．
villagers from time to time
C．
vast land
D．
heavy woods
(2)
They couldn’t land because ________．
[ ]
A．
the mud on the shore was too soft
B．
the forest was too thick to let them go through
C．
they could not find the mark on the map
D．
they could not find anyone to lead them out of the forest
(3)
The passage infers that the forest was ________．
[ ]
A．
rich of fruits and animals to be served as food
B．
not very thick as they could advance slowly by cutting the branches
C．
full of various dangerous beings
D．
full of ancient trees
(4)
The most proper title for this passage might be ________．
