Our solar system might be crazier than we once thought.Scientists say that deep within Uranus（天王星） and Neptune（海王星）it rains diamonds.
   On Earth，diamonds form under extreme heat and pressure.The inside of Uranus and Neptune also has high temperatures and pressures.What's more，the blue planets are largely made up of icy water and gases such as methane（甲烷）.
   So scientists have long believed that deep inside the two planets，the heat and pressure turn the methane into hydrogen（氫）and carbon（碳）.Then diamond rain would form，falling toward the center of the planets.
   But no one could prove that this would really work-until now.In a study published recently in the journal Nature Astronomy，scientists say they were able to create this kind of "diamond rain" in a lab，reported The Guardian.
   Scientists used high-powered lasers to create pairs of shockwaves through a kind of plastic.The plastic is made from hydrogen and carbon，much like methane.The shockwaves created high pressure and heat，like that inside Uranus and Neptune.
   "The experimental time is very short，" Dominik Kraus，lead author of the study，told The Guardian. "That we saw this very clear signature of diamonds was actually very，very surprising."
   The diamonds created in the lab were tiny，only a few nanometers（納米）wide.Scientists believe that diamonds would be much larger within Neptune and Uranus.Then they might slowly sink toward the planet's center because of gravity.

（1）What factors are needed to form diamonds？

C

C

A．Icy water and gases.
B．Hydrogen and carbon.
C．Extreme heat and pressure.
D．High-powered lasers.
（2）What does the underlined word mean in the last paragraph？

D

D

A．Unsuccessful.
B．Natural.
C．Real.
D．Small.
（3）How did scientists prove the theory of forming diamond？

B

B

A．By giving examples.
B．By doing experiments.
C．By explaining statistical data.
D．By stating argument.
（4）What can be referred from the text？

B

B

A．There are many high-powered lasers in Neptune and Uranus.
B．Scientists long believe that there are diamonds inside Neptune and Uranus.
C．The shockwaves inside Neptune and Uranus crate high pressure and heat.
D．Deep inside Neptune and Uranus could be full of diamonds.