简述动圈传声器的工作原理。

妨碍公务罪：是指以暴力、威胁方法阻碍国家机关工作人员依法执行职务，阻碍人民代表大会代表依法执行代表职务，阻碍红十字会工作人员依法履行职责的行为。或者故意阻碍国家安全机关依法执行国家安全工作任务，未使用暴力、威胁方法、造成严重后果的行为。 下列符合妨碍公务罪特征的一项是( )

A．李某让其在派出所值班的儿子回家过年

B．小刘因丈夫在公安局工作繁忙，夫妻离多聚少，因而坚决不同意丈夫在假期上班

C．非典时期某厂领导纠集大批职工阻止医务人员进入厂区隔离厂长家刚从北京回来的大学生儿子

D．派出所的老张平日横行乡里，一次在其胡作非为时被群众殴打

女，35岁，半年前母突然病故，此后失眠、情绪低沉、不愿与人交往。近3个月来独处时常听见有声音对她讲话，说母病故与某人有关，故多次给公安机关写信反映母被害之事，后来又感到自己的思维、情感不由自己支配，自己的想法还未说出已人人皆知，常独自哭泣。神经系统检查未见异常，有慢性肝炎病史3年，目前肝功 ALT80U/L。

该患者治疗首选的药物是( )。

A．氯硝安定

B．氟西汀

C．氯丙嗪

D．丙咪嗪

E．利培酮

流计装置试件厚度的限制包括（）。

A、热板和冷板间允许的最大间距

B、热板和冷板间允许的最小间距

C、试件的最小厚度

D、试件的最大厚度

有下列（）情形的纳税人，必须自行申报。

A.从两处或两处以上取得工资、薪金所得的

B.取得应税所得，没有扣缴义务人的，如个体工商户从事生产、经营的所得

C.分笔取得属于一次劳务报酬所得、稿酬所得、特许权使用费所得、财产租赁所得的

D.取得应纳税所得，扣缴义务人未按规定扣缴税款的

E.税务主管部门规定必须自行申报的

For years Internet merchants have poured millions of dollars into new technologies to make their sites easier to use. So why aren’t online customers happier

Customer satisfaction levels have remained almost fiat through the last several years. The problem, according to Larry Freed, chief executive of a consulting and research firm called ForeSee Results, is not so much that consumers have ignored the many improvements made in recent years. Rather, be said, they still expect more from Internet shopping than it has delivered.

"If we walk into a local store, we don’t expect that experience to be better than it was a couple years ago," Mr. Freed said. "But we expect sites to be better. The bar goes up every year." In ForeSee’s latest survey, released last month, just five e-commerce sites registered scores higher than 80 out of 100, and no site scored higher than 85. It was much the same story a year ago, when just five scored higher than 80, with no site surpassing 85. "Scores have inched up over time for the best e-commerce companies, but the overall numbers haven’t moved drastically," Mr. Freed said. "At the same time though, if you don’t do anything you see your scores drop steadily."

That dynamic has been a challenge for online merchants and investors, who a decade ago envisioned. Internet stores as relatively inexpensive (and therefore extremely profitable) operations. Now some observers predict a future where online retailers will essentially adopt something like the QVC model, with sales staff pitching the site’s merchandise with polished video presentations, produced in a high-tech television studio.

QVC.com is evolving in that direction. The Web site, which sold more than $1 billion in merchandise in 2006, has for the last five years let visitors watch a live feed of the network’s broadcast. But in recent months, QVC.com has also given visitors the chance to watch archives of entire shows, and in the coming months visitors will be able to find more video segments from recent shows, featuring individual products that remain in stock. Bob Myers, senior vice president of QVC.com, said the Web site’s video salesmanship is especially effective when combined with detailed product information, customer reviews and multiple photographs.

About eight months ago, for instance, a customer said that she could not determine the size of a handbag from the photographs on the site because she could not tell the height of the model who was holding it. Within two weeks the site tested and introduced a new system, showing the bags with women of three different heights. The results were immediate: women who saw the new photographs bought the bags at least 10 percent more frequently than those who had not.

Still, Mr. Myers said, video is a critically important element to sales. "E-commerce started with television commerce," he said. "The sites who engage and entertain customers will be winning here in the near future." Such a prospect is not necessarily daunting to other e-commerce executives. Gordon Magee, head of Internet marketing for Drs. Foster & Smith, based in a Rhinelander, Wis., said a transition to video "will be seamless for us." The company, Mr. Magee said, has in recent weeks discussed putting some of its product on video "so customers could see a 360-degree view they don’t have to manipulate themselves.

It can be inferred from the passage that（）

A. some people used to regard E-commerce as profit-loaded

B. E-commerce is no longer exploitable in terms of profit

C. QVC envisioned the adoption of videos in Sales a decade ago

D. polished video presentations must be made in a high-tech studio