对土地的私有权垄断（） A.是级差地租产生的原因 B.是级差地租产生的条件 C.是绝

LKJ在以下哪种状态下运行时，一定无常用制动功能。（）

A.在减速区运行

B.在站内停车控制时

C.调车状态

D.在长期慢行区段运行

肝癌手术适应症不包括

A．诊断明确，估计病变局限于一叶或半肝者

B．肝功能代偿良好

C．凝血酶原时间不低于正常的30％

D．无明显黄疸，腹水或远处转移者

E．心、肺和肾功能良好

(B)

You can tell the age of a tree by counting its ring. But these records of a tree’s life really say a lot more. Scientists are using tree ring to learn what’s been happening on the sun’s surface for the last ten thousand years. Each ring represents a year of growth. As the tree grows, it adds a layer to its trunk, taking up chemical elements from the air. By looking at elements in the rings from a certain years, scientists can tell what elements were in the air that year. Dr. Stevenson is analyzing one element, carbon-14, in ring from both living and dead tree. Some ring go back almost ten thousand year to the end of the Ice Age. When Stevenson followed the carbon-14 levels changed with the intensity of solar burning. You see, the sun has cycles. Sometimes it bums fiercely, and at other times it is relatively calm. During the sun’s violent periods, it throw off charged particles in fast moving streams called "solar winds". The particularly interfere with the formation of carbon-14 on earth. When there is more solar wind activity, less carbon-14 is produced. Ten thousand years of tree ring 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.

What do we learn from the passage about solar wind activity（）

A. It affects the growth of trees.

B. It has been increasing since the Ice Age.

C. It is determined by the chemicals in the air.

D. It follows a certain cycle.

什么情况下严禁动火？

特种劳动防护用品必须具有“三证”和“一标志”，即生产许可证、产品合格证、 ( )和安全标志。

A．安全等级证

B．安全鉴定证

C．安全评价人员资格证书

D．安全技术证