[单项选择]-The cars give off a great deal of waste gas in the streets.
-Yes. But I'm sure something will be done to ______air pollution.

[单项选择]-The cars give off a great deal of waste gas in the streets.
-Yes. But I'm sure something will be done to ______air pollution.

[单项选择]--The cars give off a great deal of waste gas in the streets.
--Yes. But I'm sure something will be done to ______ air pollution.
A. reduce
B. remove
C. collect
D. warn

[单项选择]They put both cars in exactly the same position they had been in in order to ______.


A. make it clear who should answer for the accident
B. cheat the police
C. get paid for the car damage
D. cheat the insurance company

[单项选择]The increase in the number of cars may give rise to air pollution.
A. invent
B. cause
C. lead
D. decrease

[单项选择]The Portuguese give a great deal of credit to one man for having promoted sea travel, that man ______ prince Henry the navigator, who lived in the 15th century.
A. was
B. was called
C. calling
D. being

[单项选择]

Sparks created in a lab give off X-rays, scientists announced Monday.
X-rays are a byproduct (副产物) of high-energy electron discharges in the Sun, in exploding stars, and even in lightning. Many scientists did not expect sparks alone to do the trick.
Researchers at Florida Institute of Technology brought their equipment, which had detected X-rays in lightning, into the lab. Half the team expected to see X-rays and the other half did not.
In sparks of 1.5 million to 2 million volts, the researchers indeed recorded X-rays that were remarkably similar to those produced by lightning.
"This amazed us, It opens the door to answering really big questions about lightning by generating it in the lab," said team member Hamid Rassoul. "It also tells us that we have a lot’ to learn about how even small sparks work."
X-rays are a form of electromagnetic radiation, on a spectrum (频谱) that runs from radio waves on the low
A. Scientists Created X-rays in a Lab.
B. Sparks, a New Way to Produce X-rays.
C. Runaway Breakdown Triggers New Questions.
D. Scientists Surprised by X-rays from Lab Lightning.