西藏研究生考生注意!2021研究生报名时间预计!

在以下哪种货币制度下各国货币汇率是浮动的？

A.布雷顿森林体系
B.牙买加体系
C.欧洲货币联盟
D.金本位制

某工程师为了解一台天平的精度，用该天平对一物体的质量做n次测量，该物体的质量μ是已知的，设n次测量结果X1，X2，…，Xn相互独立且均服从正态分布N(μ，σ^2).该工程师记录的是n次测量的绝对误差Zi=｜Xi-μ｜(i=1，2，…，n)，利用Z1，Z2，…，Zn估计σ.
　　(Ⅰ)求Z1的概率密度；
　　(Ⅱ)利用一阶矩求σ的矩估计量；
　　(Ⅲ)求σ的最大似然估计量.

Many experts believe that in the new world of artificial intelligence（AI）human beings will still be needed to do the jobs that require higher-order critical,creative,and innovative thinking and the jobs that require high emotional engagement to meet the needs of other human beings.The 1 for many of us is that we do not excel at those skills because of our natural cognitive and emotional tendencies:We are confirmation-seeking thinkers and ego-affirmation-seeking defensive reasoners.We will need to overcome those tendencies 2 take our thinking,listening,relating,and collaborating skills to a much higher level.This process of 3 begins with changing our definition of what it means to"be smart."4,many of us have achieved success 5 being"smarter"than other people as 6 by grades and test scores,beginning in our early days in school.AI will change that because there is no 7 any human being can outsmart,8,IBM's Watson,at least without augmentation,Smart machines can process,9,and recall information faster and better than we humans.10.AI can pattern-match faster and produce a wider array of alternatives than we can.AI can even learn faster.In an age of smart machines,our old definition of what makes a person smart doesn't 11.What is needed is a new definition of being smart,one that 12 higher levels of human thinking and emotional engagement.The new smart will be determined not by what or how you know 13 by the quality of your thinking,listening,relating,collaborating,and learning.Quantity is 14 by quality.We will spend more time training to be open-minded and learning to update our beliefs in 15 to new data.We will practice 16 after our mistakes,and we will invest more in the skills traditionally 17 with emotional intelligence.The new smart will be about trying to overcome the two big 18 0f critical thinking and team collaboration:our ego and our fears.Doing so will make it easier to perceive reality as it is,rather than as we 19 it to be.In short,we will embrace humility.That is 20 we humans will add value in a world of smart technology.
6选？

A.designed
B.characterized
C.measured
D.discovered