Question

 

Pretoria．South Africa—Hundreds 0f swimmers Play in the water along a South African beach．Suddenly a huge shark appears offshore and heads for the bathers．Before it can get close to the swimmers，the shark，for some mysterious reason，starts swimming parallel to the beach．Then it turns away from shore and heads out to sea，leaving the swimmers untouched．

Such a scene will soon become common along shark infested（鲨鱼出没）shores．An electrical engineer from the University of Pretoria has developed an electrical system that repels（击退）sharks by controlling their movements．Confused by this action，the sharks end up turning away from the beach．

In this unusual shark repellent method，an insulated（绝缘）cable is buried on the bottom of the sea around a beach from which people swim．When an electric current is sent though the cable，an electric field is produced in the water above the cable．

When the shark swims into the electric field，nerve cells just below the shark’s skin detect the field．The electricity produces a reflex（反射）action in the shark’s muscles，causing the dangerous animal with sharp teeth to swim parallel to the cable．Contused by increasing loss of control of its muscles，the shark suddenly changes its direction and heads seaward，away from the electric field．   

In a test of the invisible new shark-repellent system，a cable was placed around a beach in St．Lucia an island in the tropics．A protective net，which had been installed around the beach a long time ago to keep sharks from swimmers，was left in place during the experiment．

When the electric field was 1eft on for more than a year and a half，no sharks were found in the nets．However,when the power was turned off，89 sharks ended up in the nets．

Using the electric wall method instead of nets to protect bathers would avoid the needless death of many sharks，say biologists．Currently，thousands of sharks die each year when they become trapped in protective nets that surround holiday resorts in Africa and Australia．About 10 to 15 humans are killed by sharks annually．

1.In the first passage，why doesn’t the shark attack the swimmers？

A．Because they are many swimmers in the water．

B．Because the shark doesn’t want to eat the swimmers。

C．Because of some mysterious reason from the God．

D．Because there is an invisible electric field confusing the shark．

2.An electrical engineer from the University of Pretoria has developed         ．

A．A protective net                     B．A new shark-repellent system

C．The electric field                       D．An insulated cable

3.An electric field is produced in the water above the cable          ．

A．only when the shark swims into the electric field

B．an insulated cable is buried on the bottom of the sea around a beach from which people

swim

C．only when an electric current is sent though the cable

D．only when the sharks are trapped in protective nets

4.Which of the following is NOT TRUE according to the passage?

A．Protective nets had been installed around the beach earlier than the new shark repellent system．

B．This new kind of shark repellent system wilt take place of the protective nets．

C．Thousands of sharks die and about 10 to 15 humans are killed by sharks each year in Africa and Australia since this new system was Put into use．

D．Using the electric wall method instead of nets to protect bathers would avoid the needless death of many sharks．

 

Answer 1

【答案】

1.D 考查简单逻辑推理能力。根据文章内容及an electrical system that repels sharks by controlling their movements．Confused by this action，the sharks end up turning away from the beach可知。

2.B 本题考查考生对细节信息的理解情况。根据An electrical engineer from the University of Pretoria has developed an electrical system that repels sharks by controlling their movements及下文可知。

3.C 本题考查考生对细节信息的理解情况。根据When an electric current is sent though the cable，an electric field is produced in the water above the cable可知。

4.C 根据第5、6、7三节内容可知C是错误的。