问题 单项选择题 B型题

属于DNA病毒的是()

A.甲型肝炎病毒

B.乙型肝炎病毒

C.丙型肝炎病毒

D.丁型肝炎病毒

E.戊型肝炎病毒

答案

参考答案:B

解析:乙型肝炎病毒(HBV),属嗜肝DNA病毒科。在电镜下可见到3种病毒颗粒:①Dane颗粒:是完整的HBA颗粒。分为胞膜和核心两部分,胞膜内含乙型肝炎表面抗原(HBsAg),核心部分含有环状双股DNA、DNA聚合酶(DNAP)和核心抗原(HBcAg)和e抗原(HBeAg),是病毒复制的主体;②小球形颗粒;③管状颗粒。甲型病毒性肝炎属于微小RNA病毒科;丙型肝炎病毒属于黄病毒科,为RNA病毒;丁型肝炎病毒是一种缺陷RNA病毒;戊型肝炎病毒是无包膜球形RNA病毒。乙型病毒性肝炎的传播途径包括:①母婴传播;②输血传播:输入被污染的血液和血制品;③医源性传播:使用未经严格消毒的、被HBV污染的医疗器械,如手术和牙科器械、注射器、采血针、针灸针、内镜等均可引起HBV感染;④性传播;⑤密切生活接触传播:HBV感染患者可以通过密切日常生活接触传播给家庭成员,造成HBV感染的家庭聚集现象。

阅读理解

阅读理解

     Speeding off in a stolen car, the thief thinks he has got a great catch. But he is in for an unwelcome

surprise. The car is fitted with a remote immobilizer, and a radio signal from a control centre miles away

will ensure that once the thief switches the engine off, he will not be able to start it again.

     The idea goes like this. A control box fitted to the car contains a mini-cellphone, a micro-processor

and memory, and a GPS (全球定位系统) satellite positioning receiver. If the car is stolen, a coded (编

码的) cellphone signal will tell the control centre to block the vehicle's engine management system and

prevent the engine being restarted.

     In the UK, a set of technical fixes is already making life harder for car thieves. "The pattern of vehicle

crime has changed," says Martyn Randall, a security expert. He says it would only take him a few minutes

to teach a person how to steal a car, using a bare minimum of tools. But only if the car is more than 10

years old.

     Modern cars are far tougher to steal, as their engine management computer won't allow them to start

unless they receive a unique ID code sent out by the ignition (点火) key. In the UK, technologies like this

have helped achieve a 31% drop in vehicle-related crime since 1997.

     But determined criminals are still managing to find other ways to steal cars, often by getting hold of the owner's keys. And key theft is responsible for 40% of the thefts of vehicles fitted with a tracking system.

     If the car travels 100 metres without the driver confirming their ID, the system will send a signal to an

operations centre that it has been stolen. The hundred metres minimum avoids false alarms due to

inaccuracies in the GPS signal.

     Staff at the centre will then contact the owner to confirm that the car really is missing, and keep police

informed of the vehicle's movements via the car's GPS unit.

1. The remote immobilizer is fitted to a car to ________.

A. prevent car theft by sending a radio signal to the car owner

B. help the police make a surprise attack on the car thief

C. prevent the car thief from restarting it once it stops

D. allow the car to lock automatically when stolen

2. By saying "The pattern of vehicle crime has changed", Martyn Randall suggests that ________.

A. it takes a longer time for the car thief to do the stealing

B. self-prepared tools are no longer enough for car theft

C. the thief has to make use of computer technology

D. the thief has lost interest in stealing cars over 10 years old

3.________ is necessary in making a modern car tougher to steal.

A. A coded ignition key    

B. A unique ID card

C. A special cellphone signal        

D. A GPS satellite positioning receiver

4. The operations centre will first ________ after receiving an alarm.

A. start the tracking system

B. contact the car owner

C. block the car engine

D. locate the missing car

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