Do dragons exist today？Although often mistaken for a mythical（神话的）creature，we actually live among several different types of "dragons."For example，you may have seen dragonfly flying over a summer garden or read about a Komodo dragon lizard.The ocean has its share of dragons，too.
   The blue dragon is a marine（海洋的）snail without a shell.It is commonly known as a blue sea slug（海参）.This particular species of marine snail can swallow a bubble of air（which it holds in its stomach）that enables it to float upside down on the surface of the ocean.The underside of the slug is blue，and it back is a gray color.This helps to conceal it from birds flying overhead and from fish swimming below.
   Blue dragons feed on poisonous jellyfish and other similar species.When food is in short supply，they will eat each other.They collect toxins（毒素）from the jellyfish and store it in many finger-like structures.This ability to store poison gives them a much stronger sting（刺）than the jellyfish itself.They use this poison as a defense against enemies.The sting can also be felt by people.
   These creatures are rarely visible for study and observation except for when they come close to land during times of onshore winds.They have been seen in Hawaii and in tropical （热带）waters around the world.Beware（当心）of the blue dragon's sting!

（1）What's the purpose of the first paragraph？

A

A

A．It gives details about the topic.
B．It introduces the subject.
C．It introduces the author.
D．It gives examples of mythical monsters.
（2）What does the underlined word "conceal" in the second paragraph mean？

D

D

A．Discover.
B．Notice.
C．Protect.
D．Hide.
（3）How does the coloring of the blue sea slug provide protection？

C

C

A．It floats right side up so the blue faces down in the water.
B．Its gray coloring makes it look the same as ocean waves.
C．Its blue underside and its gray back help it not be seen from above and below.
D．It gives off blue poison into the water to protect it from enemies.
（4）What's the blue dragon's main defense against enemies？

B

B

A．It floats upside down in the water.
B．It stores poison and stings enemies.
C．It feeds on poisonous jellyfish.
D．It moves to coastal waters during times of onshore winds.
（5）Which of the following facts about the animal is true according to the passage？

D

D

A．The animal has the word "dragon' as part of its name because it is a mythical creature.
B．We can only see types of"dragons"in oceans.
C．A bubble of water in its stomach enables it to float upside down.
D．The creature are not commonly seen by people for study and observation.