About half a billion people depend on the ecosystems created and sustained by corals.And with climate change threatening coral's survival，marine scientist Enric Sala had a goal that might have seemed impossible.
   "We wanted to get into a time machine，go back hundreds of years and actually see a coral reef like they used to be everywhere，before we started exploiting them and polluting them and killing them all over the world，"Sala said.
   The goal was made possible during an expedition Sala led in 2009.The team traveled to a corner of the South Pacific Ocean，to see if the vibrant reefs there held any clues that could help them understand how to bring damaged reefs in other parts of the ocean back to health.
   "The bottom was covered by thriving（茂盛的） coral.Vivid colors surrounded me—purples，reds，oranges，yellows and greens.It was so beautiful，"Sala said.
   His team presented their findings to officials in the island country of Kiribati.The government took steps to protect the waters from fishing and other human activity.But between 2015 and 2016，record levels of ocean warming damaged half the coral reefs the team had been studying.
   After hearing that news，they lost hope for the health of coral reefs.Last year，they went in for another dive.Despite the reported conditions，the reef had somehow restored itself，filled with life and color once more.Sal a and his team were overjoyed.This is something that Sala says can be owed to two key factors.
   The first is，thankfully，half of the corals didn't die.Despite the rise in temperatures，there were enough surviving corals left behind to help reproduce the reefs.The second was the Kiribati government's decision to fully protect those waters.
   "It has an abundance of fish.So they were eating all the algae（藻類） that would smother（窒息）the dead coral skeletons and make it impossible for the corals to come back.Luckily，other places like the Caribbean also witness the good change，"Sala explained.

（1）What unlikely goal does Sala have？

D

D

A．Schooling people to protect corals.
B．Preventing people from damaging corals.
C．Appealing to people to deal with climate change.
D．Going back to the past when corals were thriving.
（2）What led to the restoration of the coral reefs？

C

C

A．Half of the damaged coral reefs restored themselves.
B．A flood of fish ate all the algae covering the dead corals.
C．The government protected waters and survival corals multiplied.
D．The government took measures to stop fishing and human activity.
（3）What can we learn about the Caribbean from Sala's words？

B

B

A．It hardly offers enough nutrition to fish.
B．It has also suffered large losses of corals.
C．It is impossible for the corals to come back.
D．It has an abundance of algae.
（4）What can be the most suitable title for the text？

A

A

A．How Did the Coral Reefs Restore？
B．Where Are the Damaged Coral Reefs？
C．What Does Biodiversity Show in the Ocean？
D．What Are the Disadvantages of Climate Change？