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Passage 1: 为什么蝙蝠携带致命病毒,自己却安然无恙? Where did novel coronavirus come from? As COVID-19 spreads throughout China and the rest of the world, an important question has yet to be answered: where did the virus come from? The latest study indicated that pangolins ( 穿山甲 ) may be an intermediate host of the virus, according to Xinhua. However, bats are suspected to be the original cause. “We don’t know the source yet, but there’s pretty strong evidence that this is a bat origin coronavirus,” said Peter Dazsak, president of EcoHealth Alliance, an environmental nonprofit , according to The New York Times. “When you look at the genetic sequence ( 基因序列 ) of the virus, and you match it up with every known coronavirus, the closest relatives are from bats,” Dazsak also told CNN. So why are bats the source of so many deadly kinds of viruses but they don’t suffer from any symptoms? As the only flying mammal ( 哺乳动物 ) with a long lifespan ( 寿命 ), bats’ body temperature is high, similar to a fever. It’s this fact that may contribute to bats’ unique immune system ( 免疫系统 ) in protecting them from the ill effects of viruses. But are bats truly to blame for the virus – or should we be blaming ourselves? Whether we destroy the forests where bats live or they end up on our plate, it’s the fault of humans for decreasing the distance between us and virus-carrying bats. Bats are an important animal in our ecosystem ( 生态系统 ) when it comes to pollinating ( 授粉 ) many fruits such as mangoes and bananas. We need to allow them to continue pollination and keep them away from our markets and mouths. 1. What can we learn about the origin of COVID-19? A. Bats have been confirmed to be its original cause. B. Pangolins are now considered the most likely source. C. It’s identified by comparing sources of various viruses. D. The virus was found to be genetically similar to those seen in bats. 2. Why don’t bats suffer from the coronavirus? A. Bats have a unique immune system. B. Their low body temperature protects them. C. Bats are the only flying mammal to live in groups. D. Living in caves helps bats fight against viruses. 3. What is the main point the author makes in the last paragraph? A. Virus-carrying bats should be killed. B. Humans should stay away from bats. C. Bats benefit but also harm our ecosystem. D. Bats could spread viruses during pollination.
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【单选题】一批产品100件,有80件正品,20件次品,其中甲生产的为60件,有50件正品,10件次品,余下的40件均由乙生产。现从该批产品中任取一件,记A=“正品”,B=“甲生产的产品”则P(B|A)=()
A.
0.625
B.
0.562
C.
0.458
D.
0.83
【单选题】以下说法中错误的是( )[中]
A.
金属材料的强度越高,抵抗变形和断裂的能力越强
B.
拉伸强度实验中,当拉伸力达到屈服点后保持不变时,试样仍能继续伸长
C.
常见金属材料判断塑性的指标为伸长率与断面收缩率
D.
加工零件的表面粗糙度值越高,则疲劳强度越大
【多选题】电子商务的安全技术主要有()。
A.
信息加密技术
B.
数字签名
C.
数字证书
D.
保密技术
【判断题】金属材料的断后伸长率和断面收缩率越大,则此材料的塑性越好
A.
正确
B.
错误
【多选题】电子商务的安全技术主要有
A.
数据加密技术
B.
数字签名技术
C.
认证机构技术和数字证书
D.
安全认证协议及其他安全技术
【单选题】以下说法中错误的是( )
A.
金属材料的强度越高,抵抗变形和断裂的能力越强
B.
拉伸强度实验中,当拉伸力达到屈服点后保持不变时,试样仍能继续伸长
C.
常见金属材料判断塑性的指标为伸长率与断面收缩率
D.
加工零件的表面粗糙度值越高,则疲劳强度越大
【单选题】以下说法中错误的是( )。
A.
金属材料的强度越向,抵抗变形和断裂的能力越强
B.
拉伸强度实验中,当拉伸力达到屈服点后保持不变时,试样仍能继实伸长
C.
常见金属材料判断塑性的指标为伸长率与断面收缩率
D.
加I零件的表面粗精度值越高,则披劳强度越大
【多选题】电子商务的安全技术主要有()
A.
信息加密技术
B.
数字签名
C.
数字证书
D.
保密制度
【单选题】以下说法中错误的是( )。
A.
金属材料的强度越高,抵抗变形和断裂的能力越强
B.
拉伸强度实验中,当拉伸力达到屈服点后保持不变时,式样仍能继续伸长
C.
常见金属材料判断塑性的指标为伸长率与断面收缩率
D.
加工零件的表面粗糙度值越高,则疲劳强度越大
【单选题】一批产品100件, 有80件正品, 20件次品, 其中甲厂生产的为60件, 有50件正品,10件次品, 余下的40件均由乙厂生产. 现从该批产品中任取一件, 记A={正品},B={甲厂生产的产品}, 则P(B|A)与P(A|B)分别是()。
A.
5/6,5/6
B.
5/8,5/8
C.
5/8,5/6
D.
5/6,5/8
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