题干

设z= 10
i
3
+
i
,则z的共轭复数为(   )

A:﹣1+3i

B:﹣1﹣3i

C:1+3i

D:1﹣3i

上一题 下一题 0.0难度 选择题 更新时间:2015-03-27 11:54:31

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D

同类题2

任务型阅读

    The increasing environmental problems and need for eco-friendly products and services are creating a new job section of green-collar jobs.____It is expected that by 2025 about 25% of the jobs in developed countries will be of green-collar jobs. Doesn't the data look promising for the future?

    ____And jobs will pop up at every income level, from environmental manager to gardener. For example, many countries including the United States have understood that fossil fuels have negative effect on the environment which can later become a serious danger to mankind.____The increasing demand of newer resources has created the need for experts and researchers who can find better ways to deal with the ongoing needs. In addition, in order to meet the increasing demand of environment-friendly equipment, both green product designer and trained workers are needed. Management of environmental organizations also demands a large number of environmental managers.

    ____ Internet is undoubtedly the best way to find information on almost any matter. Nowadays, different kinds of jobs are being posted online. Search through a couple of job websites to look for a bright future in energy conversion and recycling of waste management. Check regularly and find the right work for yourself.____

A. People who read newspapers can also find different kinds of green-collar jobs.

B. People who take green careers will be well paid.

C. Where can you find green-collar jobs?

D. Green-collar jobs have become a bright career chance for all.

E. Many countries have realized the importance and need for energy-saving products and services.

F. Therefore, possibilities are being explored to find alternatives to meet demands in a better way.

G. Forget the blue–collar and white–collar categories.

同类题4

好的养分管理可以兼顾作物高产和生物资源的保护.试验区油菜田发生的杂草有看麦娘、日本看麦娘、菵草、牛繁缕、小飞蓬等杂草.研究者将油菜田划分为不施肥、纯施氮肥、单施化肥(NPK平衡施肥)、化肥配施猪粪、化肥配施油菜桔杆五个小区进行研究.长期不同施肥方式对油菜田杂草群落物种多样性研究结果如表:

多样性指标

施肥处理

不施肥

纯施氮肥

单施化肥

化肥配施猪粪

化肥配施油菜桔杆

物种丰富度

9.0

11

5.0

7.3

8.3

辛普森多样性指数

0.29

0.23

0.52

0.53

0.89

物种均匀度

0.68

0.70

0.48

0.44

0.13

(1)油菜田中能进行生殖的所有看麦娘个体含有的全部基因,称为看麦娘的____ .看麦娘、日本看麦娘、菵草、牛繁缕、小飞蓬等杂草的差异体现了____ 多样性.

(2)对研究结果进行分析,下列说话不正确的是____ (多选)

A.辛普森多样性指数随物种均匀度增大而增大

B.合理施肥能保证杂草物种多样性,又能控制杂草的危害

C.纯氮肥区的物种丰富度最高,说明此区域物种多样性最大

D.去除所有杂草,促进油菜快速生长是本研究的研究目标

(3)试验区旁有一块地,其内鼠群有少数个体趾间有轻微的蹼,后来环境改变成为沼泽,多年以后,该鼠群中大多数个体有趾蹼,下列解释正确的是____ 

A.此时新的物种已经产生

B.环境的定向选择使有蹼的基因频率逐渐增大

C.为了适应环境的变化,无蹼鼠逐渐长出了趾蹼

D.环境导致无蹼基因突变为有蹼基因.