阅读下面的文言文，完成小题。

    管仲夷吾者，颍上人也。少时常与鲍叔牙游，鲍叔知其贤。管仲贫困，常欺鲍叔，鲍叔终善遇之，不以为言。已而鲍叔事齐公子小白，管仲事公子纠。及小白立为桓公，公子纠死，管仲囚焉。鲍叔遂进管仲。管仲既用，任政于齐，齐桓公以霸，九合诸侯，一匡天下，管仲之谋也。

    管仲曰：“吾始困时，常与鲍叔贾，分财利多自与，鲍叔不以我为贪，知我贫也。吾尝为鲍叔谋事，而更穷困，鲍叔不以我为愚，知时有不利也。吾尝三仕三见逐于君，鲍叔不以我为不肖，知我不遭也。吾尝三战三走，鲍叔不以我为怯，知我有老母也。公子纠败，召忽死之，吾幽囚受辱，鲍叔不以我为无耻，知我不羞小节而耻功名不显於天下也。生我者父母，知我者鲍子也！”

    鲍叔既进管仲，以身下之。子孙世禄于齐，有封邑者十余世，常为名大夫。天下不多管仲之贤，而多鲍叔能知人也。

    管仲既任政相齐，以区区之齐在海滨，通货积财，富国强兵，与俗同好恶。故其称曰：“仓廪实而知礼节，衣食足而知荣辱。上服度，则六亲固；四维不张，国乃灭亡。下令如流水之原，令顺民心。”故论卑而易行，俗之所欲，因而予之；俗之所否，因而去之。

    其为政也，善因祸而为福，转败而为功。贵轻重慎权衡于柯之会桓公欲背曹沫之约管仲因而信之诸侯由是归齐。

（节选自《史记•管晏列传》）

【中外历史人物评说】阅读下列材料，回答问题。

材料一：大凡一个主义，都有理想与实用两面。例如民主主义的理想，不论在哪一国，大致都很相同。把这个理想适用到实际的政治上去，那就因时、因所、因事的性质，有些不同。社会主义，亦复如是。他那互助友谊的精神，不论是科学派、空想派，都拿他来作基础。把这个精神适用到实际的方法上去，又都不同。我们只要把这个那个的主义，拿来作工具，用以为实际的运动，他会因时、因所、因事的性质情形生一种适应环境的变化。

——李大钊《再论问题与主义》

材料二：李大钊曾经与五四时期许多先进知识分子一样，信仰过空想社会主义并且真诚地为之进行种种试验，希望依此建立理想的新社会。所不同的是，李大钊最早觉悟，认识到空想社会主义道路在中国走不通，毅然选择了马克思主义和十月革命的道路。随后他以马克思主义的唯物史观为武器，对各种空想社会主义进行批判，成为一个彻底的科学社会主义者并为它在中国的实现奋斗终生。

——韩一德、李帆《从空想到科学的转变——略论李大钊早期社会主义思想》

    Driving in Canada is similar to driving in many parts of the United States. Distances and speeds, however, are posted in kilometers per hour and some signs, particularly in Quebec, may only be in French.

    Unless otherwise posted, the maximum (最大限度的) speed limit in Canada is 50km/hr in cities and 80km/hr on highways. On rural highways, the posted speed limit may be 100km/hr. It is illegal to take automobile radar detectors (汽车雷达检测器) into Quebec, Ontario, Manitoba, and the Yukon. Seat belt use is required by law for all passengers, and child car seats must be used by children under 40 pounds. Some provinces require drivers to keep their vehicles' headlights on during the day and some have banned (禁止) driving while using a hand-held cell phone. Motorcycles cannot share a lane (车道), and safety helmets for motorcycle riders and passengers are necessary. Running a red light is a serious crime throughout Canada and drivers are advised to stop before starting when a light turns green.

    Winter travel can be dangerous due to heavy snowfalls and icy conditions. Some roads and bridges are often closed in winter. Snow tires are required in some provinces. Travelers should also be careful about animals while driving at night in rural areas.

    Highway 401, from Detroit to Montreal, is one of the busiest highways in North America. It has been the scene of many deadly traffic accidents due to sudden and severe weather changes, high rates of speed, and heavy truck traffic. Thus drivers should be alert while travelling here.

    Please refer to our Road Safety page for more information. Also, we suggest that you visit the website of Canada's national authority responsible for road safety.

等轴双曲线C的中心在原点，焦点在x轴上，C与抛物线$y^2=16x$的准线交于A,B两点，$\left|AB\right|=4\sqrt{3}$，则C的实轴长为（     ）