魏知古，深州陆泽人。方直有雅才，擢进士第。以著作郎修国史，累迁卫尉少卿，检校相王府司马。神龙初，为吏部侍郎，以母丧解。服除，为晋州刺史。睿宗立，以故属拜黄门侍郎，兼修国史。

    会造金仙、玉真观，虽盛夏，工程严促，知古谏曰：“臣闻‘古之君人，必时视人之所勤，人勤于食则百事废’，故曰‘不作无益害有益’。又曰‘罔咈百姓以从己之欲’。此皆兴化立治、为政养人之本也。今为公主造观，将以树功祈福，而地皆百姓所宅，卒然迫逼，令其转徙，扶老携幼，剔瓦，呼嗟道路。乖人事，违天时，起无用之作，崇不急之务，群心震摇，众口藉藉。陛下为人父母，欲何以安之？愿下明诏，顺人欲，除功役，收之桑榆，其失不远。”不纳。复谏曰：“自陛下戡翦凶逆，保定大器，苍生颙颙以谓朝有新政。今风教颓替日益甚，府藏空屈，吏员浸增，诸司试补、员外、检校官已赢二千，太府之帛为殚，太仓之米不支。臣前请停金仙、玉真，讫亦未止。今前水后旱，五谷不立，繇兹向春，必甚饥馑，陛下欲何方以赈之？又突厥于中国为患自久虽遣使请婚恐豺狼之心弱则顺伏强则骄逆月满骑肥若乘中国饥虚窥犯亭鄣复何以防之?”帝嘉其直，以左散骑常侍同中书门下三品。

    先天元年，为侍中。从猎渭川，献诗以讽，手制褒答，并赐物五十段。明年，封梁国公。窦怀贞等诡谋乱国，知古密发其奸，怀贞诛，赐封二百户，物五百段。玄宗恨前赏薄，手敕更加百户，旌其著节。是冬，诏知东都吏部选事，以称职闻，优诏赐衣一副。自是恩意尤渥，由黄门监改紫微令。与姚崇不协，除工部尚书，罢政事。开元三年卒，年六十九。宋璟闻而叹曰：“叔向古遗直，子产古遗爱，兼之者其魏公乎！”赠幽州都督，谥曰忠。

（节选自《新唐书•魏知古传》）

    You're in a department store and you see a couple of attractive young women looking at a sweater．You listen to their conversation：

    “I can't believe it－Lorenzo Bertolla! They are almost impossible to find．Isn't it beautiful? And it's a lot cheaper than the one Sara bought in Rome．”

    They leave and you go over to see this incredible sweater．It's nice and the price is right．You've never heard of Lorenzo Bertolla, but those girls looked really stylish．They must know．So, you buy it．You never realize that those young women are employees of an advertising agency．They are actually paid to go from store to store, talking loudly about Lorenzo Bertolla clothes．

    Every day we notice what people are wearing, driving and eating．If the person looks cool, the product seems cool, too．This is the secret of undercover marketing．Companies from Ford to Nike are starting to use it．

    Undercover marketing is important because it reaches people that don't pay attention to traditional advertising．This is particularly true of the MTV generation－consumers between the age of 18 and （3）It's a golden group．They have a lot of money to spend, but they don't trust ads．

    So advertising agencies hire young actors to “perform” in bars and other places where young adults go．Some people might call this practice misleading, but marketing executive Jonathan Ressler calls it creative．“Look at traditional advertising．Its effectiveness is decreasing．”It is true, because everyone knows an ad is trying to persuade you to buy something．However, you don't know when a conversation you overhear is just a performance．

如图所示电路，闭合开关S后，发现灯L₁不亮，L₂正常发光。此电路的故障可能是（）