1 . In times of stress, particularly when the water gets too warm, the coral(珊瑚)erupts the algae(海藻), and the coral turns white, causing a state called coral bleaching(漂白). Just a few degrees of heat can lead to coral bleaching, putting the coral on a path to starvation and death.

Driven by climate change, marine heat waves are becoming one of the greatest threats to the existence of coral, which is important to the ocean ecology. But in some rare good news researchers have discovered coral can recover from bleaching even before a heat wave ends, suggesting it has the potential to survive long heat waves. Coral was thought to survive only if a heat wave lasted just a few weeks.

But no one had studied this process during a longer heat wave. Then in 2015, Julia Baum, a marine ecologist at the University of Victoria, began a survey of two common species: brain and star coral around Kiritimati in the central Pacific Ocean. They checked the condition of the coral as the heat wave struck and disappeared.

Starting in May 2015, the temperature rose about 1 ℃ within 2 months. As expected, coral that housed heat-sensitive algae bleached sooner than those housing the heat-tolerant kind of algae. As the water continued to warm, even heat-tolerant algae erupted.

Many brain and star coral on Kiritimati recovered from bleaching while the water was still unusually warm. Baum said, "The unexpected recovery provides new hope, because it means that even under lasting heat waves, there's a path forward for some of them."

An unusual feature of the recovery is that brain coral that started out with heat-sensitive algae had a higher survival rate(82%)than coral that began with heat-tolerant algae(25%). "That finding is surprising," said Baum, expecting that heat-tolerant algae would be better suited for helping coral survive a heat wave. But during a longer heat wave, it might be more advantageous to start with a heat-sensitive algae.

1. What results in coral bleaching?

A．The white algae.	B．The coral's death.
C．An attack of waves.	D．A rise in ocean temperature.

2. Why did Baum begin the survey?

A．To prove that coral can stop climate change.

B．To study how coral bleaching comes about.

C．To figure out whether coral survives long heat waves

D．To explain why coral bleaching is a big threat to coral

3. How did Baum feel about the finding?

A．Ashamed.	B．Confused
C．Worried.	D．Astonished.

4. What can the finding be used to do?

A．Protect the ocean environment.	B．Reduce coral bleaching.
C．Grow more different algae.	D．Regulate the heat wave.