题目

已知命题：关于的函数的定义域是；命题：当时，恒成立. 如果命题“”是真命题，“”是假命题，求实数的取值范围. 答案：解.若是真命题，则关于的不等式在上恒成立，所以 时，满足题设； 时，要使在上恒成立，必须，解得.， 综上. 若是真命题，则恒成立 ，所以 ，当且仅当，即时取等号。 ，  或 若命题“”是真命题，“”是假命题，则命题和一真一假 所以的取值范围是。Every year billions of pounds are spent on hair loss treatment. If we succeed in curing hair loss with 3D printed hair follicles(毛囊), it will be a huge revolution.L’Oreal, the cosmetics firm is partnering with a French bio-printing company called Poietis, which has developed a form of laser(激光) printing for cell-based objects. Poietis’ technique begins with the creation of a digital map that determines where living cells and other tissue components should be placed to create the desired biological structure. This involves how the cells are expected to grow over time. The file based on the digital map is then turned into instructions for the printing equipment, so that it can lay down tiny droplets made out of the cell-based "bio ink" one layer at a time. The printing process involves bouncing a pulsing laser off a mirror and through a lens, so that when it hits a ribbon(色带) containing the bio ink, a droplet of the matter falls into place. About 10,000 of these micro-droplets are created every second.It typically takes about 10 minutes to print a piece of skin 1cm wide by 0.5mm thick. However, since hair follicles are complex and consist of 15 different cells in a structure, they may take longer.Poietis is not the only company working on bio-printing, but most others use another way, which involves pushing a bio-ink through a nozzle(喷嘴), rather than lasers to build their tissue. Poietis suggests its technique puts less stress on the biological matter, meaning there is less risk of causing it damage.Alopecia UK—a charity that provides support and advice about hair loss—has mixed feelings about the development. “It is encouraging to know that companies such as L’Oreal are investing in technology that may help those with hair loss in the future,” said spokeswoman Amy Johnson.“However, we would suggest it’s still very early to be getting excited about what this potentially could mean for those with medical hair loss. At this point it is unclear as to whether this technology could benefit those with all types of hair loss.”“Also, if this new technology does lead to a treatment option, given the high costs of existing hair transplant procedures, how many people will be able to realistically afford any new technological advances that may become available? As with any other research and development into processes that may be able to help those with hair loss, we watch with great interest.”1.What does Paragraph 2 mainly tell us?A. How the printing process is carried out.B. Where the living cells should be placed.C. How long the cells are expected to grow.D. What the printing equipment is made up of.2.What does the underlined word “it” in Paragraph 4 refer to?A. hair follicleB. biological matterC. nozzleD. bio-ink3.The passage implies that the new technology may ______.A. meet some practical challengesB. help people with hair loss at presentC. offer solutions to all problems of hair lossD. cost a large sum of money to transplant hair4.What is Amy Johnson’s attitude towards the new technology?A. Disapproving.B. Optimistic.C. Cautious.D. Negative.