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【单选题】
Read the section "Dangerous Chemicals Were Dumped In The River." Select the paragraph that explains what type of pollutants got into the Bronx River.A.
A turtle's health can say a lot about the river's health. That's because turtles live a long time. Plus, they generally stay put. The turtle constantly takes in its environment. This gives pollutants in a river plenty of time to build up in the turtles' bodies, Sykes explains.
B.
The Bronx River was once clean. Native Americans used to fish in it. The river's health changed by the 1850s. That's when it was pumped full of garbage, sewage and other waste. It became full of dangerous chemicals called PCBs, lead and mercury.
C.
In the 1960s and 1970s the government cracked down on these chemicals. They could no longer be used as much. It helped make the Bronx and other rivers a little bit cleaner.
D.
How clean? When Sykes got the turtles' tests back from the lab, he didn't see any signs of mercury.
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举一反三
【简答题】根据铸铁中石墨形态的不同,铸铁可分为 、 、 、 。
【简答题】根据石墨形态,铸铁可分为()、( ) 、() 和( )
【单选题】奥氏体不锈钢熔化极氩弧焊一般采用( )富氩混合气体保护.
A.
Ar+0.5-1%O2
B.
Ar+1-5%O2
C.
Ar+5-10%O2
D.
Ar+10-15%O2
【单选题】Queations 1 and 2 are based on the news report you have just heard.
A.
It crawled over the woman's hands.
B.
It wound up on the steering wheel.
C.
It was killed by the police on the spot.
D.
It was covered with large scales.
【单选题】奥氏体不锈钢熔化极氩弧焊一般采用()富氩混合气体保护。
A.
Ar+0.1-0.2%O2
B.
Ar+0.5-1%O2
C.
Ar+1-5%O2
D.
Ar+5-10%O2
【单选题】Queations 1 and 2 are based on the news report you have just heard.
A.
Annoyed
B.
Scared.
C.
Confused.
D.
Offended.
【简答题】根据石墨形态不同,灰口铸铁可分为 、 、 、 。
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