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The locust (蝗虫) is a kind of insect. Though it is small, it can cause great trouble to plants and people.
The locust usually does things alone. 1． But, sometimes something changes the way nature works. When the number of locusts increases somewhere and there are lots of plants to eat, the locusts get together in “swarms(一大群)”.
2． It is found in Africa, the Middle East, and Asia — in about 60 countries altogether. When desert locusts swarm, so many plants and people in the world get in trouble.
A swarm of desert locusts can be 1200km2 in size. 3． And there can be 50 million locusts in each square kilometers. Each locust eats its own weight in plants every day, and a swarm of desert locusts can eat more than 150 million kilos of food in one day. 4． In 1954 a swarm of locusts from northwest Africa flew thousands of miles to finally land in Great Britain!
It’s the desert locusts that cause major agricultural damage (农业损失) and brings hunger to people all over the world. 5．
| A．Imagine an area that is over 20 kilometers wide and 50 kilometers long, full of locusts! |
| B．They can also fly very long distances (距离). |
| C．It lives its own and eats on its own. |
| D．Perhaps the most dangerous locusts is desert locusts. |
| E．It’s no wonder that farmers in many countries fear it more than the snakes and the spiders. |
同类型试题
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
