问题 选择题

某种玉石的主要成份是NaAlSi2O6。关于NaAlSi2O6的说法正确的是

A.相对分子质量为202克

B.该物质由9个原子构成

C.该物质中含有二种金属元素

D.该物质中钠元素与氧元素质量比为1:6

答案

答案:C

A、化合物NaAlSi2O6相对分子质量=23+27+28×2+16×6=202;相对分子质量无单位,故A不正确;

B、根据物质的化学式NaAlSi2O6,该物质由Na、Al、Si、O四种元素组成,该物质的分子由9个原子构成;故B不正确;

C、根据物质的化学式NaAlSi2O6,该物质由Na、Al、Si、O四种元素组成,其中Na、Al两种为金属元素;故C正确;

D、该物质NaAlSi2O6中钠元素与氧元素质量比=23:(16×6)=23:96≠1:6;故D不正确;

故选C.

阅读理解

They leap from helicopters or speeding boats, bringing aid to swimmers who get into trouble off Italy’s popular beaches.

Hundreds of specially trained dogs from Italy’s corps of canine(犬类的) lifeguards set out each summer to help swimmers in need of rescue.

These "life dogs" wear a harness that victims can grab to be dragged back to shore, and unlike human lifeguards, they can easily jump from helicopters and speeding boats to reach swimmers in trouble.

With millions flocking to Italy’s crowded beaches each summer, the Italian Coast Guard says it rescues about 3,000 people every year —and their canine helpers have saved several lives.

It takes three years for the canines to reach expert rescue status, and currently 300 dogs are fully trained for duty, said Roberto Gasbarri, who directs the Italian School of Canine Lifeguards program.

"Dogs are of good physical strength. They can increase the speed at which victims are rescued," Gasbarri said.

"The dog becomes a sort of intelligent lifebuoy(救生圈). It is a buoy that goes by itself to a person in need of help, and comes back to the shore also by himself, choosing the best landing point and swimming through the safest currents," he said.

The school will train any breed, as long as they weigh at least 30 kilograms, but New found lands and golden retrievers are most commonly used because they are good at swimming. Each dog works together with a human lifeguard, who also acts as the animal’s trainer.

"Being retrievers, they set out to pick up anything we tell them, be it a human being, an object, or a fish, and they bring it back to the shore," said lifeguard Monia Luciani. "They do not associate it with a physical activity, but it is rather a game for them."

小题1:The dogs wear a harness so that __________.

小题2:The dogs are helpful to _________.

小题3:Why does the school usually choose to train the New found lands and golden retrievers?

___________________________________.

小题4:How do the dogs regard the pickup training?

____________________________________.

单项选择题