单选题 Just a two-hour trek from Australia"s Queensland coast lies the largest coral reef system in the world. In the very early days, people thought of it as one continual reef running all the way down the Queensland coast. It"s only been latterly that we"ve discovered that it"s lots of individual reefs, around about 2,900 separate reef systems which make up the Great Barrier Reef(大堡礁).
Just exactly how does the reef come by all this coral? Coral is animals while most people think they"re plants. They look like plants; they sit and sway in the currents. But, in fact, they"re animals. In other words, much of the Great Barrier Reef is an actual living creature.
Coral is basically a jellyfish, which has stopped wandering the oceans, has the ability to pull calcium (钙)carbonate(碳酸盐) out of the surrounding water, lays down a limestone(石灰岩) cup, hence forming the large reef system here. When you look at a coral, you are really looking at very thin coral colony (群体)over centuries and centuries of coral skeletons.

单选题 Which of the following is TRUE according to the passage?

A、 The largest coral reef system in the world is a two-hour trek from Australia"s Queensland.
B、 Coral is plants because they sit and sway in the currents.
C、 All of the Great Barrier Reef is an actual living creature.
D、 The Great Barrier Reef is the largest coral reef in the world.

单选题 How do the large reef systems form?

A、 limestone cup forms the large reef systems.
B、 Coral pulls calcium carbonate out of the surrounding water and lays down a limestone cup.
C、 Jellyfish stopped wandering the oceans, hence forming the large reef systems.
D、 Coral skeletons form the large reef systems.