搜题请搜索小程序“爱下问搜题”
问题 填空题
已知直线l的参数方程为
x=3t
y=4t+m
（t为参数），圆C的极坐标方程为ρ=2cosθ，若直线l与圆C有唯一公共点，则m的值为______．
答案

直线l的普通方程为4x-3y+3m=0，圆C的直角坐标方程为x2+y2-2x=0．

所以圆心C（1，0）到直线l的距离d=

|4+3m|
5
=1．

解得m=

1
3
或-3．

故答案为：

1
3
或-3．

单项选择题

根据《环境保护法》的规定，下列哪一项是县级以上人民政府环境保护行政主管部门的职权

A．对国家环境质量标准中未作规定的项目，制定地方环境质量标准
B．对国家污染物排放标准中未作规定的项目，制定地方污染物排放标准；对国家污染物排放标准中已作规定的项目，制定严于国家污染物排放标准的地方污染物排放标准
C．定期发布环境状况公报
D．会同有关部门对管辖范围内的环境状况进行调查和评价，拟订环境保护规划
查看答案
单项选择题

The "standard of living" of any country means the average person’s share of the goods and services which the country produces. A country’s standard of living, (1) , depends first and (2) on its capacity to produce wealth." Wealth" in this sense is not money, for we do not live on money (3) on things that money can buy. "Goods" such as food and clothing, and "services" such as transport and " (4) ". A country’s capacity to produce wealth depends upon many factors, most of (5) have an effect on one another. Wealth depends (6) a great extent upon a country’s natural resources. Some regions of the world are well supplied with coal and minerals, and have a fertile soil and a (7) climate; other regions possess none of them.

Next to natural resources (8) the ability to turn them to use. China is perhaps as well (9) as the USA in natural resources, but suffered for many years from civil and (10) wars, and (11) this and other reasons was (12) to develop her resources. (13) and stable political conditions, and (14) from foreign invasion, enable a country to develop its natural resources peacefully and steadily, and to produce more wealth than another country equally well (15) by nature but less well ordered.

A country’s standard of living does not only depend upon the wealth that is produced and consumed (16) its own borders, but also upon what is indirectly produced through international trade. (17) , Britain’s wealth in foodstuffs and other agricultural products would be much less if she had to depend only on (18) grown at home. Trade makes it possible for her surplus manufactured goods to be traded abroad for the agricultural products that would (19) be lacking. A country’s wealth is, therefore, much influenced by its manufacturing capacity, (20) that other countries can be found ready to accept its manufactures.

2（）

A.primary

B.principal

C.foremost

D.uniquely
查看答案