设,ab∈R, 则"(a-b)a2<0"是“a
设向量a1=（1 1 2）T，a2=（2 t 4）T，a3=（t 3 6）T，a4=（0 2 2t）T。若向量组{a1，a2，a3，a4}的秩是3，矩阵A=（a1 a2 a3）的秩是2，则参数t=（）。
When did the steamboat "New Orleans" make its first trip？
In （）.
A few years ago I had an "aha!" moment regarding handwriting.
I had in my hand a sheet of paper with handwritten instructions on it for some sort of editorial task. It occurred at first that I did not recognize the handwriting, and then I realized whose it must be. I finally became aware of the fact that I had been working with this colleague for at least a year, maybe two, and yet I did not recognize her handwriting at that point.
It was a very important event in the computerization of life—a sign that the informal. Friendly communication of people working together in an office had changed from notes in pen to instant messages and emails. There was a time when our workdays were filled with little letters, and we recognized one another’s handwriting the way we knew voices or faces.
As a child visiting my father’s office, I was pleased to recognize, in little notes on the desks of his staff, the same handwriting I would see at ho
A. talk more about handwriting
B. take more notes on workdays
C. know better one another’s handwriting
D. communicate better with one another
"高钙牛奶"折桂香港
90年代中期香港牛奶公司先后分别以"新鲜牛奶"、"脱脂牛奶"的定位将产品推向市场，但销售业绩平平。这种定位与当时市场众多的牛奶品牌定位十分趋同，很难吸引消费者的关注。一份消费者调查资料显示，相当多的香港人开始意识到钙元素在预防骨质疏松症中的重要作用。这给牛奶公司的策划人提供了灵感：何不在牛奶中加入钙质，推出"高钙牛奶"-这对当时的香港人来说仍是一个全新的产品概念。另外，一些消费者担心喝含脂牛奶会摄入过多脂肪，而低脂牛奶通常又不够鲜美，因此，"高钙牛奶"还必须具有脱脂且味美的特点，才可能赢得市场机会。
牛奶公司的调研表明，在香港，有骨质疏松隐患的人以25-40岁女性居多。基于"高钙牛奶"能预防骨质疏松症的功效及脱脂、味美的特点，牛奶公司决定在这一阶段年龄的女性中寻找目标市场。"高钙牛奶"作为当时的一种全新产品，只有创新型消费者才可能尝试购买，而通常受过教育又具有较高收入的人才可能具有创新精神，成为创新型消费者。综合以上考虑，最后牛奶公司把目标消费者定为年龄在25-40岁的、受过教育的、有较高收入的女性。
"高钙牛奶"很快被生产出来并集中铺在许多主要街区的超市连锁店-目标顾客经常光顾的地方。在定价方面，考虑到消费者可能不愿为一个新产品付出高价而否定了撇脂定价；又害怕采取渗透定价使产品形象受到损害，所以最终采取了折衷定价方式，将价格定在主要竞争者的平均价格水平上。
牛奶公司的"高钙牛奶"电视广告非常成功，广告中，中青年妇女骨质疏松的隐患用一种高雅的方式表现出来，而产品的利益承诺也是用一种直接的、非常可信的方式传递给广告受众。虽然广告费投入不大，但效果很好：品牌认知率和广告认知率分别高达87%和76%.除电视广告外，牛奶公司还在香港各大报纸和杂志上刊登了广告，更详尽、全方位地展开了"高钙牛奶"的功效-强身健体。
牛奶公司向全港1800多名医生与营养专家发送了宣传资料（有关骨质疏松症和产品介绍宣传单），希望通
已知a，b是实数，则a＞b。
（1）a2＞b2（2）a2＞b（）
It has been justly said that while "we speak with our vocal organs we (1) with our whole bodies," All of us communicate with one another (2) , as well as with words. Sometimes we know what we’ re doing, as with the use of gestures such as the thumbs - up sign to indicate that we (3) But most of the time we’ re not aware that we’ re doing it. We gesture with eyebrows or a hand, meet someone else’ s eyes and (4) . These actions we (5) are random and incidental. But researchers (6) that there is a system of them almost as consistent and comprehensible as language, and they conclude that there is a whole (7) of body language, (8) the way we move, the gestures we employ, the posture we adopt, the facial expression we (9) , the extent to which we touch and the distance we stand (10) each other. The body language serves a variety of purposes. Firstly it can replace verbal commun
A. as if
B. as
C. when
D. like
设包含4个数据元素的集合S={"do"，"for"，"repeat"，"while"}，各元素的查找概率依次为：p1=0.35，p2=0.15，p3=0.15，p4=0.35。将S保存在一个长度为4的顺序表中，采用折半查找法，查找成功时的平均查找长度为2.2。请回答：
若采用链式存储结构保存S，且要求平均查找长度更短，则元素应如何排列应使用何种查找方法查找成功时的平均查找长度是多少
If those "mad moments"—when you ’can’t remember what your friend has told you or where you left your keys—are becoming more frequent, mental exercises and a healthy brain diet may help.
Just as bodies require more maintenance with the passing years, so do brains, which scientists now know show signs of aging as early as the 20s and 30s. "Brain aging starts at a very young age, younger than any of us had imagined and these processes continue gradually over the years," said Dr. Gary Small, the director of the Center on Aging at the University of California, Los Angeles. "I’m convinced that it is never too early to get started on a mental or brain-fitness program," he added.
In his book, The Memory Bible, the 51-year-old neuroscientist (神经学家) lists what he refers to as the 10 suggestions for keeping the brain young. They include training memory, building skills, reducing stress, mental exercises; brain food
A. writing with one’s left hand
B. learning a foreign language
C. doing crossword puzzles
D. taking pictures
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