根据短文内容，从短文后的七个选项中选出能填入空白处的最佳选项.选项中有两项为多余选项.
Mystery of Evolution
Following the outbreak of the novel coronavirus pneumonia(NCP), also named COVID-19 by WHO, there is a general fear of the unknown virus as its full effects remain to be seen. Fever, coughing, sore throat, difficulty breathing-the NCP's symptoms are similar to the common cold or the flu. but it's potentially more dangerous.
Viruses could be deadly, like HIV and Ebola (埃博拉) . But what are viruses? How can they cause so much trouble? Viruses are non-living organisms (有机体) approximately one-millionth of an inch long. Unlike human cells or bacteria, they can't reproduce on their own. ___46___
Viruses can infect every living thing-from plants and animals down to the smallest bacteria. For this reason, they always have the potential to be dangerous to human life. Sometimes a virus can cause a disease so serious that it is fatal. Other viral infections cause no noticeable reaction. Viruses lie around our environment all of the time, waiting for a host cell to come along. They can eater our bodies by the nose, mouth, eyes or breaks in the skin. ___47___For example, HIV, which causes AIDS. attacks the T-cells of the immune system.
But the basic question is, where did viruses first come from?____48____"Tracing the origins of viruses is difficult. " Ed Rybicki, a virologist at the University of Cape Town in South Africa, told Scientific American, "because viruses don't leave fossils (化石) and because of the tricks they use to make copies of themselves within the cells they've invaded." ___49___First, viruses started as independent organisms, then became parasites (寄生者) . Second. viruses evolved from pieces of DNA or RNA that "escaped" from larger organisms. Third, viruses co-evolved with their host cells, which means they existed alongside these cells.
For the time being, these are only theories. The technology and evidence we have today cannot be used to test these theories and identify the most plausible explanation. ___50___ Or future studies may reveal that the answer is even murkier (含糊不清的) than it now appears.
A. Once inside, they try to find a host cell to infect.
B. Until now, no clear explanation for their origin exists.
C. Continuing studies may provide us with clearer answers.
D. There's pretty strong evidence that this is a bat origin coronavirus.
E. However there are three main hypotheses (假说) to explain the origin of viruses.
F. Instead, they invade the cells of living organisms to reproduce, spread and take over.
G. Bat is a flying mammal with a long lifespan, whose temperature is high, similar to a fever.
【答案】46. F 47. A 48. B 49. E 50. C
【解析】
这是一篇说明文。作者通过这篇文章主要向我们讲述了新型冠状病毒以及病毒侵害人体的原理。
【46题详解】
上文Unlike human cells or bacteria, they can't reproduce on their own.(不像人类细胞或细菌，他们不能通过自己繁殖)与F. Instead, they invade the cells of living organisms to reproduce, spread and take over.(相反，他们入侵生物组织的细胞进行繁殖、扩张和占据)承接自然，上下文是明显的转折关系，reproduce是关键词，故选F项。
【47题详解】
上文They can eater our bodies by the nose, mouth, eyes or breaks in the skin.(他们可以通过鼻子、嘴、眼睛或皮肤的伤口处进入我们的身体)与A. Once inside, they try to find a host cell to infect.(一旦进入，他们就会找一个宿主细胞来感染)承接自然，上下文讲述的话题一致，enter和inside是关键词，故选A项。
【48题详解】
上文But the basic question is, where did viruses first come from? (但最基本的问题是，病毒最初是来自哪儿)与B. Until now, no clear explanation for their origin exists.(直到现在，他们的原始存在没有明确的解释)承接自然，选项中的their就是上文提到的virus，origin exists和first come from是关键词，故选B项。
【49题详解】
E. However, there are three main hypotheses (假说) to explain the origin of viruses.(但是，有三个解释病毒起源的主要假说)与下文内容提到的三点在文章结构上构成总分关系，故选E项。
【50题详解】
下文Or future studies may reveal that the answer is even murkier (含糊不清的) than it now appears.(或者将来的研究会揭示这个问题比现在更加含糊不清)与C. Continuing studies may provide us with clearer answers.(继续的研究会给我们提供更清晰的答案)承接自然，上下文构成明显的选择关系，answer是关键词，故选C项。
Mystery of Evolution
Following the outbreak of the novel coronavirus pneumonia(NCP), also named COVID-19 by WHO, there is a general fear of the unknown virus as its full effects remain to be seen. Fever, coughing, sore throat, difficulty breathing-the NCP's symptoms are similar to the common cold or the flu. but it's potentially more dangerous.
Viruses could be deadly, like HIV and Ebola (埃博拉) . But what are viruses? How can they cause so much trouble? Viruses are non-living organisms (有机体) approximately one-millionth of an inch long. Unlike human cells or bacteria, they can't reproduce on their own. ___46___
Viruses can infect every living thing-from plants and animals down to the smallest bacteria. For this reason, they always have the potential to be dangerous to human life. Sometimes a virus can cause a disease so serious that it is fatal. Other viral infections cause no noticeable reaction. Viruses lie around our environment all of the time, waiting for a host cell to come along. They can eater our bodies by the nose, mouth, eyes or breaks in the skin. ___47___For example, HIV, which causes AIDS. attacks the T-cells of the immune system.
But the basic question is, where did viruses first come from?____48____"Tracing the origins of viruses is difficult. " Ed Rybicki, a virologist at the University of Cape Town in South Africa, told Scientific American, "because viruses don't leave fossils (化石) and because of the tricks they use to make copies of themselves within the cells they've invaded." ___49___First, viruses started as independent organisms, then became parasites (寄生者) . Second. viruses evolved from pieces of DNA or RNA that "escaped" from larger organisms. Third, viruses co-evolved with their host cells, which means they existed alongside these cells.
For the time being, these are only theories. The technology and evidence we have today cannot be used to test these theories and identify the most plausible explanation. ___50___ Or future studies may reveal that the answer is even murkier (含糊不清的) than it now appears.
A. Once inside, they try to find a host cell to infect.
B. Until now, no clear explanation for their origin exists.
C. Continuing studies may provide us with clearer answers.
D. There's pretty strong evidence that this is a bat origin coronavirus.
E. However there are three main hypotheses (假说) to explain the origin of viruses.
F. Instead, they invade the cells of living organisms to reproduce, spread and take over.
G. Bat is a flying mammal with a long lifespan, whose temperature is high, similar to a fever.
【答案】46. F 47. A 48. B 49. E 50. C
【解析】
这是一篇说明文。作者通过这篇文章主要向我们讲述了新型冠状病毒以及病毒侵害人体的原理。
【46题详解】
上文Unlike human cells or bacteria, they can't reproduce on their own.(不像人类细胞或细菌，他们不能通过自己繁殖)与F. Instead, they invade the cells of living organisms to reproduce, spread and take over.(相反，他们入侵生物组织的细胞进行繁殖、扩张和占据)承接自然，上下文是明显的转折关系，reproduce是关键词，故选F项。
【47题详解】
上文They can eater our bodies by the nose, mouth, eyes or breaks in the skin.(他们可以通过鼻子、嘴、眼睛或皮肤的伤口处进入我们的身体)与A. Once inside, they try to find a host cell to infect.(一旦进入，他们就会找一个宿主细胞来感染)承接自然，上下文讲述的话题一致，enter和inside是关键词，故选A项。
【48题详解】
上文But the basic question is, where did viruses first come from? (但最基本的问题是，病毒最初是来自哪儿)与B. Until now, no clear explanation for their origin exists.(直到现在，他们的原始存在没有明确的解释)承接自然，选项中的their就是上文提到的virus，origin exists和first come from是关键词，故选B项。
【49题详解】
E. However, there are three main hypotheses (假说) to explain the origin of viruses.(但是，有三个解释病毒起源的主要假说)与下文内容提到的三点在文章结构上构成总分关系，故选E项。
【50题详解】
下文Or future studies may reveal that the answer is even murkier (含糊不清的) than it now appears.(或者将来的研究会揭示这个问题比现在更加含糊不清)与C. Continuing studies may provide us with clearer answers.(继续的研究会给我们提供更清晰的答案)承接自然，上下文构成明显的选择关系，answer是关键词，故选C项。
苏19057182-3号