A
The evolution(进化) of animals depends upon the environmental conditions on Earth.Here are the top four oldest animal species on Earth.
Horseshoe Crab—445 million years old
Horseshoe crabs appeared on Earth 445 million years ago.They live in shallow ocean waters across the world.Horseshoe crabs have a long tail.They have nine eyes in total，found throughout the body.Out of the nine，two large eyes are mainly used by horseshoe crabs and the others are used to control their movements.
Nautilus—500 million years old
The nautilus is a kind of shellfish living in the sea that existed 500 million years ago.That is long before dinosaurs appeared on Earth.It is said to be the only surviving member of a large group of shellfish.Nautiluses live at a depth of 2，200 feet in the ocean.
Jellyfish (水母)—550 million years old
Jellyfish with an umbrella-like head can be found in every ocean in the world.They have no brain or nervous system.Jellyfish are found in different shapes and colors.The 90 percent of their body weight is water.They are also known to eat other jellyfish.The box jellyfish is the most dangerous species of jellyfish on Earth.
Sponge—580 million years old
Sponges are a special kind of creature living in the sea that looks like a plant.They appeared in the world's oceans 580 million years ago.There are 5，000 different species of sponges in the world.They live at different depths in the oceans.
Sponges don't have arms or head.They have a special power to grow back a lost body part and a new sponge will grow from the old one.The body of sponges contains many channels，which become a shelter for many small species.
【语篇解读】 动物的进化取决于地球的环境条件。当我们挖掘地球的历史时，我们可以看到一些动物物种在很久很久以前便出现在地球上并繁衍至今。以下列出了地球上四大最古老的动物物种。
1．How many eyes does a horseshoe crab have?
A．One. B．Two.
C．Seven. D．Nine.
D [细节理解题。根据Horseshoe Crab—445 million years old中“They have nine eyes in total...”可知马蹄蟹(horseshoe crab)有九只眼睛。]
2．What is the similarity between the nautilus and sponges?
A．Both have long tails.
B．Neither of them has a head.
C．Both can live in the deep sea only.
D．Both existed before dinosaurs appeared on Earth.
D [推理判断题。根据Nautilus—500 million years old中“That is long before dinosaurs appeared on Earth.”可知鹦鹉螺(nautilus)在恐龙出现在地球上之前就已经存在了。又根据Sponge—580 million years old可知海绵(sponge)先于鹦鹉螺出现在地球上。]
3．What do we know about jellyfish from the text?
A．They can be found in most rivers.
B．Their body is mostly water.
C．Their head looks like a plant.
D．They don't have arms or a head.
B [细节理解题。根据Jellyfish(水母)—550 million years old中“The 90 percent of their body weight is water.”可知水母(jellyfish)体内含有百分之九十的水分。]
