如果a$÷$b（b≠0）的商是负数，那么(     )

【历史上重大改革回眸】阅读下来，回答问题

材料一：一，“军功者各以率（标准）受上爵，为私斗者各以轻重被刑”；二，“宗室非有军功论，不得为属藉（列入家族谱牒）”；三，“明尊卓爵秩等级，各以差次名田宅（按等级分享田宅），臣妾衣服以家次”；四，“有军功者显蒙，无军功者虽富无所芬华（荣耀）”。这四条法令对秦国的历史可以说产生了划时代的影响。

——朱绍侯《商鞅变法与秦国早期军功爵制》

材料二：魏初风俗至陋，……迁都之后，于革易旧俗，亦可谓雷厉风行。……民族根柢，莫如语言，语言消灭，未有不同化于他族者。孝文以仰慕中国文化之故，至欲自举其语言而消灭之，其改革之心，可谓勇矣。其于制度，亦多所厘定。

——吕思勉《两晋南北朝史》

材料三：北魏在中原建立以后，所面临的最大问题即如何处理这一广大地区的民族关系，其中包含如何对待汉族的先进生产方式、汉族的文化问题。是继续保存拓跋氏旧的社会制度和旧有的文化习惯，还是摒弃旧俗，接受先进的文化，在新的历史环境中获得新生，北魏的统治者必须作出抉择。

——白寿彝《中国通史》

我国古代的伟大工程蕴含着中华民族文化与精神的底蕴。隋朝时修筑的促进南北经济文化交流的重要工程是（    ）

材料一：******在党的十九大报告中指出，增进民生福祉是发展的根本目的。要在幼有所育、学有所教、劳有所得、病有所医、老有所养、住有所居、弱有所扶上不断取得新进展，保证全体人民在共建共享发展中有更多获得感。

材料二：2017年各地人大把关注民生、保障和改善民生作为依法履职的出发点和落脚点。对教育、卫生、社保等人民群众最关心、反映最强烈的突出问题，组织人大代表集中视察或通过代表小组开展执法检查、专题调研，为人大代表提出有质量的关注民生议案、建议创造条件。在调研方法上，注意上下联动，并把听取汇报、实地视察、走访群众、召开关注民生座谈会等方式有机结合起来。同时，对相关部门工作开展跟踪督查，对热点问题进行专题询问等，保证了热点、难点问题得到较快和较好的解决。

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

Don'tyou just love ice skating every winter? I am sure that since winter isapproaching, your skates are set to come out, just waiting to be used. Impressyour friends with a new trick on how to ice­skate backwards with the help ofthese trips.

Stand straight

 The first thing that you need to do is standstraight.____， if you feel that you are falling backwards. Don't worry；this happens to all.

 Confidence is what you need

Themost important step while learning how to skate backwards is having enoughconfidence in yourself and in what you are doing. How can you achieve this? Bypractice. One of the important ice skating tips and techniques is that if youfeel that you are losing your balance, then scissor (做剪式运动) your skates____.

 Maintain speed

 Try sculling with one skate while rolling in astraight line with the

 other____.Now bring the skate which you are using to scull, and then again,repeat the same process. Make sure that you put most of your weight on theskate which is moving straight and not the one with which you are sculling.Now, try the same thing using the other foot.

____

 Once you are confident that you can scull witheither foot, the next thing that you have to do is increase your speed. Trysome of your own tricks now. Scull with either foot or with both at the sametime.

 Scull and be aware

 While you keep one foot straight, keepsculling with the other. You can do that with both feet at the same time.____，but don't get so involved that you don't see where you are going. If you arenot watching your back, you might just bang into something or someone.

A．That is, keep pushing yourself backwards with an outwardstroke(滑动)

B．While going backwards, just get used to the feeling ofmoving backwards

C．Keep practicing this till you are confident about it

D．Increase your speed now

E．One must be brave enough to learn to ice­skate backwards

F．Concentrate on what you are doing

G．Just put your chin up and slightly bend your knees