When scientists accidentally killed what turned out to be the world’s oldest living creature, it was bad enough. Now, their mistake has been worsened after further research found it was even older – at 507 years.
The ocean quahog, a type of deep-sea clam, was dredged (捕捞) alive from the bottom of the North Atlantic near Iceland in 2006 by researchers. They then put it in a fridge-freezer, as is normal practice, unaware of its age. It was only when it was taken to a laboratory that scientists from Bangor University studied it and concluded it was 400 years old.
The discovery made it into the Guinness Book of World Records. However, by this time, it was too late for Ming the Mollusc(软体动物), named after the Chinese dynasty when its life began. Unfortunately researchers who calculated Ming’s age killed it instantly by opening its shell.
The researchers opened the ancient clam up to judge its age by counting growth rings inside. But the rings were so close together that scientists ended up having to count the rings on the outside to be accurate, leading CBS journalists to point out that if scientists had just started there, Ming could have lived on. Now, after examining the quahog more closely, using more advanced methods, the researchers have found the animal was actually 100 years older than they first thought.
Dr Paul Butler, from the University’s School of Ocean Sciences, said: “We got it wrong the first time and maybe we were a bit hasty publishing our findings back then. But we are absolutely certain that we’ve got the right age now.” The mollusc was born in 1499 – just seven years after Columbus discovered America and before Henry VIII had even married his first wife, Catherine of Aragon in 1509.
A quahog’s shell grows by a layer every year, in the summer when the water is warmer and food is plentiful. It means that when its shell is cut in half, scientists can count the lines in a similar way that trees can be dated by rings in their trunks.
Jan Heinemeier, associate professor at the University of Denmark, who helped date Ming, told Science Nordic: “The fact that we got our hands on a 507-year-old animal is incredibly fascinating, but the really exciting thing is of course everything we can learn from studying the mollusk.”
At first, the scientists found that _____________.

A．The ocean quahog got a deadly disease

B．The growth rings inside were so close together

C．it was accurate to count the growth rings outside

D．The ocean quahog was 400 years old

Why did the scientists open the ancient clam up?

A．To count the growth rings outside of the clam.

B．To study how old the clam was.

C．To see the structure of it.

D．To give an immediate operation on it.

The sixth paragraph is mainly about_____________. 

A．How to calculate the age of a tree

B．Why a quahog’s shell grows by a layer each year

C．How to calculate the age of a quahog

D．Why a quahog likes it when the water is warmer

Which of the following is NOT true?

A．The researchers have got the right age of the ocean quahog.

B．The mollusc was born after Columbus discovered America.

C．The ocean quahog was named after the Chinese dynasty.

D．A quahog’s shell grows by a layer every season.

Where does the text probably come from?

A．A magazine of marine life.	B．A travel brochure.
C．A biography.	D．A science fiction.