单项选择题

A．Sell hot dogs or ice cream.
B．Take tickets to customers.
C．Take up special service jobs.
D．See to the company"s management.
<上一题 目录 下一题>
热门 试题

填空题
counting[听力原文]You can tell the age of a tree by countingits rings, but these records of a tree s life really say a lot more. Scientists are using tree rings to learn what s been happening on the sun s surfacefor the last ten thousand years. Each ring representsa year of growth. As a tree grows, it acids a layer to its trunk, taking up chemicalelements from the air. By looking at the elements in the rings from a given year, scientists can tell what elements were in the air that year. Doctor Stevenson is analyzingone element—carbon-14, in rings from both living and dead trees. Some of the rings go back almost ten thousand years to the end of the Ice Age. When Stevenson followed the carbon-14 trail back in time, he found carbon-14 levels change with the intensityof solar burning. You see the sun has cycles. Sometimes it burns fiercelyat other times it s relatively calm. During the sun s violentperiods, it throws offcharged particles in fast moving streams called solar winds . The particles interfere withthe formation of carbon-14 on earth. When there s more solar wind activity, less carbon-14 is produced. Ten thousand years of tree rings show that the carbon-14 level rises and falls about every 420 years. The scientists concluded that solar wind activity must follow the same cycle.
单项选择题
A．The company wants every employee to help guests enjoy the tour.B．The employees of Disney parks are very strict with themselves.C．The employees want to present their best before the guests.D．The company places the greatest emphasis on simple jobs.
A．The company wants every employee to help guests enjoy the tour.
B．The employees of Disney parks are very strict with themselves.
C．The employees want to present their best before the guests.
D．The company places the greatest emphasis on simple jobs.
相关试题