1 . Until now, scientists haven’t been able to study the new rock on the moon.The new samples from Chang’e 5 will change this. They’re from near Mons Rümker, a volcanic mountain where the rock is thought to be much younger-- about 1 billion years old.

There are a lot of reasons scientists are eager to study this younger rock, one of which is that it could help us more precisely date not only the moon, but many rocky planets and other objects.

Here’s how that works: Scientists date lunar rock by using something called a chronology curve（年代学曲线）, says Jollliff, a scientists at Washington University in St. Louis. Basically, they estimate the age of the rock by counting the number of craters（火山口） in the area the rock comes from; those increase as objects strike the rock over time. To make this estimation, scientists need to match the number of craters to a precise age. Right now, they only have data points for lunar rock that is 3 to billion years old. Modern techniques can date the new sample extremely accurately, and once scientists know its precise age, they can add a valuable data point to their chronology curve. The dating system will also help us more accurately estimate the age of all sorts of objects in space, like rocky planets and other moons.

Another reason scientists are keen to study this young volcanic rock is to find out more about how volcanism works on the moon. Jollliff says that it’s unclear why there was volcanic activity on the moon for such a long period of time. Most of the moon; s volcanic activity, he says, is thought to have occurred 3 or 4 billion years ago, when the moon was still pretty young. But since the moon does not have plate structure, which drives volcanism on Earth, it’s unclear what could have caused much later volcanic activity. “That’s something that you can find out of the samples by studying them in the lab,” Jollliff says.

1. What does the underlined word “this” in paragraph 1 refer to?

A．The fact of being unable to study the new rock.

B．The new rock from near Mons Rümker.

C．One of the reasons to study the moon;s new rock.

D．The study of the moon’s younger rock.

2. Scientists research this younger rock because they can ________.

A．ensure there was volcanic activity on the moon.

B．more precisely date only the moon.

C．date lunar rock by using a chronology curve.

D．explore how volcanism works on the moon.

3. What can we infer from the last paragraph?

A．Scientistsare keen to study this young volcanic rock.

B．Scientists can’t know why volcanic activity exists on the moon.

C．The moon’s volcanic activity occurred 3 or 4 billion years ago.

D．It’s clear what could have caused much later volcanic activity.

4. What can be a suitable title for the text?

A．How scientists study the younger rock.

B．Why the research is important.

C．Why the younger rock is worth studying.

D．What scientists do to study the younger rock.