题目内容：

    Scientists have discovered a "monster black hole" so massive that, in theory, it shouldn't exist

It’s a stellar black hole---the type that forms after stars die, collapse, and explode. Researchers had previously believed that the size limit was no more than 20 times the mass of our sun because 8S these stars die, they lose most of their mass through explosions that expel matter and gas swept away by stellar winds

This theory has now been toppled by LB-1, the newly discovered black hole. Located about 15.000 light years away, it has a mass 70 times greater than our sun, according to a press release from the Chinese Academy of Sciences.

The findings were published by Chinese researchers in the journal Nature on Wednesday.

"Black boles of such mass should not even exist in our galaxy, according to most of the current models of stellar evolution," said Liu Jifeng, head of the team that made the discovery. "LB-1 is twice as massive as what we thought possible. Now theorists will have to take up the challenge of explaining its formation."

Scientists are now scratching their heads at how LB-1 got so huge.

The Chinese team has proposed a number of theories. LB-1' sheer size suggests that it “was not formed from the collapse of only one star," the study said--- instead, it could potentially be two smaller black holes orbiting each other.

Another possibility is that it formed from “fallback supermova.” This is when a supernoma---the last stage of an exploding star---ejects material during the explosion, which then falls back into the supernova, creating a black hole.

This fallback formation is theoretically possible, but scientists have never been able to prove or observe it. If this is how LB-1 formed, then we may have "direct evidence for this process” for the first time, the study said.

There are several types of black holes and stellar black holes like LB-1 are on the smaller side, according to NASA. Supermassive black holes are much bigger---they can be billions of times the mass of our sun,

Scientists believe supermassive black holes may be connected to the formation of galaxies, as they often exist at the center of the mass star stems but it is still not clear exactly how, or which form first.

1.Why does the writer write the article?

A.To report the great achievement Chinese scientists have made in black hole theory,

B.To inform the readers of the basic knowledge about the black hole,

C.To share with the readers the new development of the black hole discovery,

D.To demonstrate the significance of discovering new black holes for science.

2.Which of the following about LB-1 is true to the passage?

A.It is the biggest black hole ever discovered,

B.It lost only a small part of its mass through explosion.

C.It couldn't have been formed from the collapse of one star,

D.Its discovery may lead to some breakthrough in the “fallback formation theory".

3.Which of the following is right according to the passage?

A.If the sun in our galaxy dies some of its mass will be taken away by stellar winds.

B.A massive supernova will be formed and then exploded if the sun in our galaxy dies.

C."The Milky Way" was formed after a supermassive black hole collapsed and exploded.

D.If “the Milky Way" dies, a supermassive black hole will be formed after its death.