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Most animals only have animals of a different kind for food. But sometimes two kinds of animals come together in a partnership which is good for them. You may have noticed some birds on the backs of sheep. This is not because they want a ride, but because they find easy food in the parasites on sheep. The sheep let the birds do so because they can stop the parasites from troubling them. So though they can do with it by themselves, they can do better together with each other.  

Sometimes an animal has a plant partner. The relationship develops until the two partners cannot do without each other. This is so in corals of the sea. Inside their bodies they have very small plants, which act as “cleaners”, taking the useless things from the coral and giving oxygen in return. That is what the animal needs to live. If the plants are killed, or are even kept from receiving light so that they cannot live as usual, the corals will die. 

Reading Comprehension:

1.Some birds like to sit on a sheep because ________. 

A. they can eat its parasites             B. they enjoy traveling with the sheep 

C. they can’t live without its parasites   D. they want to find the warm place

2. The underlined word “they” in the first paragraph means _________.

A. birds and parasites    B. birds and sheep  

C. parasites and sheep    D. birds, parasites and sheep 

3. We learn from the passage that corals need plants for _______.

A. friends    B. light    C. food    D. oxygen 

4.The Chinese for the word “oxygen” is _________.

A. 氧氣      B. 空氣    C. 廢氣     D.二氧化碳

5.What is the second paragraph mainly about? 

A. Some animals and plants cannot live without each other.

B. Some animals and plants cannot develop their friendship easily.

C. Some plants eat each other.     

D. Some animals live better together.

Key:

1A  2B  3D  4A  5 A

Background Information:

寄居蟹與�？�共生。�？�固著在寄居蟹所寄居的螺殼上，通過寄居蟹的運動而擴大其取食范圍，反過來寄居蟹可以�？�的刺細胞來防御敵害。
白蟻與鞭毛蟲共生又是一個典型的例子。白蟻的腸道為鞭毛蟲提供了生活場所，而鞭毛蟲可以幫助白蟻消化其所賴以生存的纖維。
爬行動物中的“綠毛龜”與絲狀藻類之間是共生現象的另一種形式，絲狀藻借龜甲表面，作為附生的基底，從龜甲表層分泌物中吸取養料而滋生；當整個龜甲被絲狀藻覆蓋后，形似龜甲長滿綠毛從而可逃避敵害。
燕千鳥，它充當了“牙簽”，又叫“牙簽鳥”。 鱷魚一吃東西，牙縫里就嵌進了肉屑殘質，慢慢地腐敗生蛆。燕千鳥在鱷魚的稀稀落落的牙齒中間走來走去，剔牙齒，捉蛆蟲，侍候得鱷魚舒舒服服。同時，它自己也飽餐了一頓。
世界上還有一種小鳥，和老虎是好朋友，它總是跟隨在老虎的左右飛來飛去。當老虎張開大嘴休息時，這些“小家伙”就肆無忌憚地飛進老虎口，也同樣啄食牙縫中的肉屑，成了猛虎的“朋友”。 老虎對這種小鳥非常友好，從不吞吃它。這種小鳥名叫虎雀。

Vocabulary:

partnership 伙伴關系

parasites 寄生蟲

Coral 珊瑚

Oxygen 氧氣