在计算光纤通信系统的线路中继距离时,考虑的富余度应包括()和()两部分。
参考答案:光缆富余度,光通道功率代价
被保险人以同一保险标的、同一保险利益、同一保险事故分别向两个以上保险人订立保险合同的保险称为()。
A.共同保险
B.再保险
C.重复保险
D.原保险
Directions:
The following chart shows the percentage of near-sighted students in Chinese schools. Write an essay of 160~200 words based on the chart. In the composition you should:
1) describe the situation
2) analyze the causes, and
3) give your comments.