Sea urchins（海胆）are small creatures,but what's really remarkable about them is that they eat anything that happens to float by.They have really sharp teeth they use to rid rocks of algae（海澡），which makes them pretty valuable especially in places like Hawaii where algae are threatening the coral reefs.In the summer of 2019，500，000 of them were used to deal with the algae.
The problem started when non-native algae were introduced to the ecosystem of Kane'ohe Bay in the 1970s.Because they had no enemies,they ended up taking over the bay,according to the National Marine Fisheries Service（NMFS）．The algae blocked sunlight from reaching the coral,which in turn affected the local fish because they changed the chemistry of the water.
That's when the NMFS turned to sea urchins that loved to devour the algae.But they had to grow to the size of a cherry tomato before they could be used.Since 2011，sea urchins have been grown and used to handle the algae problem.Some of the funds are available due to an unfortunate incident.
In 2005，a ship was grounded on a shallow reef near Kane'ohe Bay.When the ship was removed,20 acres of reefs have been damaged.When there is environmental damage,the NMFS and other agencies receive funds from the wrongdoers and the funds are used to restore the damage.Some funds were spent on other projects like the sea urchins.When they are large enough,divers carefully place them on the reef.
Algae isn't the only thing that threatens the coral reefs.Climate change and the effects of fishing and tourism in the area also endanger the coral reefs.But turning to sea urchins instead of man-made solutions seems like the best way to go.
Why are sea urchins regarded as outstanding creatures？ ______
A. They are tiny but have teeth.
B. They can keep the ocean clean.
C. They are useful in removing algae.
D. They grow on coral reefs with algae.
What happened after non-native algae arrived at Kane'ohe Bay？ ______
A. They helped the coral reefs to survive.
B. They spread to every corner of the bay.
C. They didn't fit in with the new surroundings.
D. They fought against other species to get food.
What does the underlined word "devour" in paragraph 3 mean？ ______
A. Eat.
B. Block.
C. Tease.
D. Attract.
What does the author suggest doing to save coral reefs？ ______
A. Relying on humans' solutions.
B. Banning fishing and tourism.
C. Employing divers to handle algae.
D. Letting nature take care of nature.
