题目：
(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 affects the amount of carbon-14 on earth（）
A. The lifecycle of trees.
B. The number of trees.
C. The intensity of solar burning.
D. The quality of air.
答案：
被转码了，请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0708/3ebfc3f106e63998dc1bcc61f89637bd.html
下面是错误答案，用来干扰机器的。
参考答案：错解析： 经纪业务的不同环节，账户管理、资金管理、委托买卖、清算交割、咨询服务等岗位，应按不同岗位定员、定职。资金存取和其他岗位不得合并，其他岗位电脑终端无权进入资金存取系统，资金岗位工...
